After serving as Professor of Physics on the Faculty of Science at the Dijon Lycée for a brief period in 1848, Pasteur transferred to Strasbourg University and, as Professor of Chemistry, continued his studies on molecular asymmetry. But it was not all work and Louis fell in love with and married Marie Laurent, the daughter of the university rector. They married on 29 May 1849 and Louis and Marie remained devoted to each other throughout their lives. The couple had five children, but sadly only two survived childhood. Marie assisted Louis in his scientific pursuits in whatever way she could, although she did complain in a letter to her father-in-law that Louis spent too much time on his experiments. Throughout the times when Louis was beleaguered by controversy, however, Marie remained steadfast.
In 1854 Pasteur was appointed Dean and Professor of Chemistry at the new Faculty of Sciences in the industrial town of Lille, the economy of which depended on its distilleries and factories. It was at Lille that Pasteur showed in a practical way that he supported the view of the Minister of Public Instruction at the university that science should not exist only for its own sake. He encouraged members of the faculty to keep up with scientific theory, to be innovative and to apply their science to the real needs of the community. In accordance with these beliefs he trained his students to assist factory managers in solving the chemical problems they encountered in their production processes.
In the summer of 1856 one Monsieur Bigot, a distiller and the father of one of Pasteur’s students, asked Pasteur for help. He and other manufacturers needed a chemist to examine why alcohol becomes contaminated with undesirable substances during fermentation. Their alcohol yields were erratic, wines unexpectedly became sour or turned to vinegar, lactic acid was sometimes produced instead of the desired vinegar and the quality and taste of beer was almost impossible to control. These problems had obvious economic consequences.
At the time that Pasteur agreed to help, the mysterious chemical processes of living animals were slowly being unravelled by scientists; Pasteur’s work on crystals had contributed to this. A German organic chemist, Friedrich Woehler, had astonished the scientific world when he synthesised the organic compound urea, showing that organic compounds could be made in a test tube whereas previously it was thought that they could only be synthesised by living animals.
The process of fermentation was, however, believed to be a straightforward chemical breakdown of sugar that occurred due to the presence of inherent destabilising vibrations that could be transferred from a vat of finished wine to new grape pressings to restart the fermentation process. The yeast cells found in the fermenting vats of wine were recognised as being living organisms, but they were believed to be either a product of fermentation or catalytic agents that assisted during fermentation. A few lone voices had concluded that yeast was the cause and not the product of fermentation but they had been ridiculed by scientific experts who dismissed any biological theory that challenged chemical explanations of molecular reaction.[9] It was precisely because of these prevailing views that the brewers’ problems had not been solved.
Pasteur’s previous work prepared him to look beyond chemical explanations. Not long after beginning his investigations in the Bigot factory, Pasteur found three clues that allowed him to solve the puzzle of alcoholic fermentation. Pasteur’s methods, and his suspicion that only living cells produced asymmetrical compounds, led him to conclude and then prove that living cells, the yeast, were responsible for forming alcohol from sugar, and that contaminating micro-organisms turned the fermentations sour. Different micro-organisms, living creatures, caused normal and abnormal fermentations in the production of wine, beer and vinegar. Pasteur was able to demonstrate this by cultivating the various micro-organisms in an appropriate sterile medium. He discovered anaerobic life, a world of micro-organisms that can live without oxygen. This is the basis of microbiology and the discovery paved the way for his study of germs that cause septicaemia and gangrene and made it possible for techniques to be devised which could kill microbes and control contamination and infection.
But Pasteur’s findings on fermentation challenged the established chemical theory of the day and brought him into direct conflict with Justus von Liebig. Liebig, nineteen years older than Pasteur, was an old-school expert in chemistry who refused to use a microscope. He dismissed Pasteur’s biological view of fermentation and putrefaction as ‘getting everything backwards’. When Pasteur criticized Liebig’s methodology, a protracted battle began.[10] As Pasteur’s reputation burgeoned so did the hostility that was directed at him and when he was proposed for a vacancy in the influential Academy of Sciences in Paris opposition came from many quarters.
According to Pasteur’s nephew, one of Pasteur’s many biographers, his uncle’s objections to others were based on the science behind their work and were never personal in nature and for this reason, his nephew concluded, Louis was incapable of understanding envy and ill-will in others. In a letter that Pasteur wrote to his wife Marie, he stated without guile or conceit that everyone knew he was a valid candidate but that many of his opponents were afraid that chemists wished to subvert all other disciplines to chemistry. He believed this to be the reason that all the naturalists were against him, ‘especially the ignorant ones’—but those in his own field were against him too.[11]
‘SIMPLE EXPERIMENT’ DELIVERS A MORTAL BLOW
In 1857, at the age of 35, Pasteur was appointed to his alma mater, the Ecole Normale Supérieure, as assistant director of both scientific studies and general administration. He moved to Paris with Marie and their three children but, despite his position, was given neither a laboratory nor funds. To continue his work on fermentation he set up a small laboratory in a ratin-fested attic.[12] Pasteur used his own money to further his work while the frenzied excitement and controversy aroused by his research on fermentation swirled about him.
The ongoing debate in the scientific world surrounding the theory of spontaneous generation was also gaining momentum not only in the exalted French Academy of Sciences. The idea that beetles, eels, maggots, and now Pasteur’s microbes could arise spontaneously from putrefying matter had been speculated upon since Greek and Roman times. Although the prevailing scientific elite supported spontaneous generation—if living tissue could turn into non-living matter then the converse should also be true—no definitive experiments had been undertaken. In January 1860 the academy offered a prize to anyone who could settle the matter.
Pasteur did not hesitate even though his colleagues and friends warned that challenging spontaneous generation could harm his reputation. Pasteur not only disputed the doctrine but took on its most prominent advocate, Félix-Archimede Pouchet. Pouchet had published a paper in 1858 and an authoritative book in 1859 on spontaneous generation and had conducted experiments that seemed to have produced micro-organisms from non-living matter. Pasteur suggested that Pouchet and other exponents of the spurious theory had achieved these results because their experimental methods were not exacting enough and germ matter from the air had contaminated their experiments.
From his work on fermentation Pasteur concluded that the yeasts and other micro-organisms that were found during fermentation and putrefaction came from the outside, via dust in the air. Pasteur designed and conducted a series of ingenious experiments that proved that if air carrying dust and dirt was excluded from a flask of nutritive broth, the broth remained pure and clear, but the same sterile solution when exposed to unpurified air or to a drop of water filled with micro-organisms was soon teeming with life.
In one experiment Pasteur showed that grape skins at the beginning of grape harvest were the source of the yeast. Grape juice extracted with sterile needles would not ferment. Covering the grape trellises to keep off contaminating dust resulted in grapes that would not produce wine. Pasteur then had to prove that contamination was carried in dust in the air. He devised the famous swan-neck flask. Air entered the flask through the opening but the curved neck trapped dust particles and micro-organisms ensur
ing the fluid within remained sterile. This showed that air alone could not trigger the growth of micro-organisms. When the flask was tipped the sterile liquid touched the contaminated walls and micro-organisms grew.
Never one to do things by halves, Pasteur worked with 60 flasks. He put twenty at the bottom of a mountain, twenty at approximately 2500 feet (762 metres) above sea level, and the remainder at the top of a glacier, at 6000 feet (1829 metres). These were the extraordinary lengths Pasteur went to in order to prove his hypothesis that it was possible to obtain air at any location in which micro-organisms would not generate spontaneously and thus dispute Pouchet’s theory.[13] The higher the altitude the less dust in the air and the fewer flasks that showed growth.
Pasteur won the challenge and announced to the scientific world that the doctrine of spontaneous generation would never recover from the mortal blow of his ‘simple experiment’. Some of Pasteur’s preparations which are kept at the Pasteur Institute in France have remained sterile for over a century and are a testament to his scientific method. In 1862 Pasteur was awarded the Academy of Sciences prize and Pouchet withdrew, but not graciously. He attacked Pasteur in a new book, accusing him of obstinacy and of not facing facts. Pasteur’s retort was that he had science and ‘true method’ on his side, not ‘fantasy and instinctive solutions’. In a lecture at the Sorbonne in 1864 Pasteur asserted that ‘there is now no circumstance known in which it can be affirmed that microscopic beings came into the world without germs, without parents similar to themselves.’[14]
Although he had opponents, the esteem that others had for Pasteur was demonstrated in 1864 when Emperor Napoleon III requested that Pasteur investigate the diseases that were afflicting wine and causing economic losses for the wine industry.[15] In a vineyard in Arbois Pasteur demonstrated that wine diseases are caused by micro-organisms that can be killed by heating the wine to 55°C for several minutes. This process, now known as ‘pasteurisation’, also killed germs in beer and milk and was soon in use throughout the world.
In his eclectic findings, published in 1866, Pasteur discussed the causes and prevention of wine diseases, described pasteurisation and explained that some organisms like yeast can exist with or without oxygen. He also explained that putrefaction, the negative side of fermentation, is caused by an anaerobic microbe, which he called ‘vibrio’.[16] Pasteur saw decay as a natural process that helps balance the environment by breaking down dead organic matter.
***
With each new phase of his work, Pasteur was compiling his dossier on micro-organisms. While continuing his study of fermentation and spontaneous generation, Pasteur was asked by the Department of Agriculture to head a commission to investigate a silkworm disease that was devastating the French silk industry. Even though initially Pasteur was unaware that silkworms suffered from disease, his research was to forge another link in his chain of discovery and save yet another industry. He began an intense five-year study in 1865.
Convinced that all putrefying processes were caused by micro-organisms, Pasteur concluded that putrefaction was destroying the silkworms. He identified at least two diseases and, elaborating on his study of fermentation, confirmed that each disease was caused by a specific foreign element, a microbe, and that the infection could be passed on.
The excessive workload and the unceasing criticism that Pasteur attracted began to take their toll and in 1868, at the age of only 46, Pasteur suffered a crippling stroke that almost ended his career. Astonishingly—and luckily, as many of his greatest discoveries were still to come—he recovered. While still partially paralysed, Pasteur completed his work on silkworms, often dictating his observations from an armchair.[17] As Pasteur regained his health so did the silk industry in France and other European countries.
It is both fascinating and astonishing that Pasteur would soon apply the findings from his landmark work on silkworms to human disease and infection and to the plight of the many women who died very soon after giving birth from puerperal fever or, as it was then commonly called, childbirth fever. This new scientific knowledge would soon bring huge benefits to humankind by establishing basic methods of sterilisation, or asepsis, to control contagion and infection, practices that would revolutionise surgery and obstetrics.
Pasteur was inching closer to formulating the Germ Theory of Disease and, the pinnacle of his achievements, finding a cure for rabies. It is almost impossible for us in the 21st century, in the age of cloning, mapping the genome and stem-cell research, to fathom the mindset of doctors who, through most of history, attributed infectious disease to foul air, harmful bodily fluids, comets and mystical forces. Pasteur was convinced that the microbes he studied were the agents of infection and he believed he had provided conclusive proof.
The discoveries that Pasteur made that saved many French industries led him to hypothesise on the possible connections between micro-organisms and disease in larger animals and humans. He proposed that micro-organisms such as bacteria, fungi and protozoan parasites did not occur spontaneously but reproduced within their own species in various ways, and that they were present in large numbers almost everywhere, in air, water and dust. Therefore germs caused fermentation, putrescence and disease, and ergo, different microbes cause different diseases. Although to us this seems exceedingly simple and indisputable, in Pasteur’s day—because the idea that a living ‘germ’ could cause a chemical reaction would be a retrograde step in scientific thought—to extrapolate that germs cause disease was seen as a nonsense.[18]
Re-enter Baron Justus von Liebig, Pasteur’s nemesis. He questioned Pasteur’s experiments and findings on Germ Theory in print in 1869. In reply, Pasteur challenged the scientific world to decide between French biology and Liebig’s German chemistry. He suggested the Royal Academy appoint a commission that would judge the validity of his experiments, but there was no response from either Liebig or the academy. Undaunted, Pasteur travelled to Munich and confronted Liebig face-to-face but the older scientist dismissed Pasteur and bluntly refused to engage in any debate.
It was no holds barred for some of Pasteur’s adversaries. The chemist and historian Marcelin Berthelot published notes written by one of Pasteur’s closest friends and colleagues, Claude Bernard, to discredit Pasteur’s Germ Theory. Following Pasteur’s methods, Bernard had used the science available to him to question Pasteur’s findings. Bernard could not have imagined that after his death these same notes would be used to publicly discredit his friend. Although distraught and reluctant to speak against the colleague he had lost and whom he still held in high regard, Pasteur, for the sake of his own reputation, refuted the accusations.
With each new sphere of research that Pasteur entered he polarised the scientific community and the greatest enmity came from doctors who were outraged and insulted by ‘this chemist’ whom they considered to be their intellectual inferior. Pasteur was attacked by members of the Academy of Medicine in Paris as a fanatic, afflicted with ‘microbial madness’.[19] But he also had his supporters. Joseph Lister, the Professor of Surgery at Glasgow University, was impressed by Pasteur’s work. Convinced of the link between micro-organisms and infection, Lister began to systematically sterilise his instruments and bandages and sprayed phenol solutions in his operating rooms. The result was a dramatic drop in the number of infections following surgery.
By the mid 1870s many physicians acknowledged that some diseases were accompanied by specific micro-organisms, but the body of medical opinion was unwilling to concede that endemic diseases like cholera, diphtheria, scarlet fever, childbirth fever, syphilis and even smallpox could ever be caused by them. Although not a physician, Pasteur was aware of the huge mortality rate associated with childbirth fever. In order to further his studies he visited hospitals and morgues to obtain samples of blood and secretions from the uteruses of Parisian mothers who had died from the fever.[20] In the cultures he identified the micro-organisms that are now called streptococci.
As Pasteur wandered through hospital wards he beca
me increasingly aware that infection was spread from sick to healthy patients by physicians and hospital workers. Pasteur, the chemist, began to hammer home this point to physicians. In a famous speech that he gave at the Academy of Medicine he stated:
This water, this sponge, this lint with which you wash or cover a wound, may deposit germs which have the power of multiplying rapidly within the tissue ... If I had the honour of being a surgeon ... not only would I use none but perfectly clean instruments, but I would clean my hands with the greatest care ... I would use only lint, bandages and sponges previously exposed to a temperature of 1300 to 1500 degrees.[21]Not all those in the medical profession were quick to embrace Pasteur’s findings or appreciated the blunt delivery of the message. Even after Pasteur had established that deadly microbes were the cause of infection, in the late 1870s an eminent physician, in a lecture to the Academy of Medicine, described childbirth fever as a metabolic disorder. Pasteur, unable to control himself, yelled from the back of the hall that it was doctors who carried microbes from sick women to healthy ones. The depth of the hostility towards Pasteur became evident when one elderly surgeon challenged him to a duel. But the medical profession soon came to accept the views of Pasteur and Lister and antiseptic medicine and surgery became the rule.
In April 1878 Pasteur presented a summary of his work to the French Academy of Sciences and made the point that the various branches of science could all gain from each other. Pasteur avowed that there was now ‘absolute proof that there actually exist transmissible, contagious, infectious diseases of which the cause lies essentially and solely in the presence of microscopic organisms.’[22] He confirmed that he had found proof that for some diseases the idea of spontaneous generation must be abandoned, as should the idea that contagion and infection suddenly originate in the bodies of humans or animals. Pasteur described the hypothesis of spontaneous generation as gratuitous, as having no basis in observation and condemned it as ‘fatal’ to medical progress.
Smallpox, Syphilis and Salvation Page 6