Father of Modern Medicine

Today is the 186^th birthday of the father of modern medicine. Louis Pasteur (1822-1895) is widely considered one of the greatest benefactors of humanity. His diligent research led to some of the greatest discoveries in the causes and prevention of contagious diseases that have saved millions of lives. His life’s work gave birth to many branches of biological science — microbiology, bacteriology, immunology, stereochemistry, virology and molecular biology.

He was single-handedly responsible for some of the most important scientific concepts and practical applications of science. The single, most important contribution to medical science and modern medical practice was the germ theory. It led to the first vaccine for rabies and development of immunizations, aseptic surgical procedures, safe fermentation and food handling, and pasteurization.

To establish the modern scientific principles of biology and biochemistry, however, he first had to take on the entire scientific community and debunk the consensus that had been widely believed for centuries: spontaneous generation (abiogenesis). Back then, it was believed that life arose spontaneously from nonliving matter, such as maggots from rotting meat, akin to diseases from bad energy or thoughts. The origins of the belief in spontaneous generation went back to the earliest philosophers, such as the Milesian philosopher Anaximander from the sixth and fifth century B.C., the Greek philosopher Aristotle from the fourth century B.C., and the German naturalist of the thirteenth century Middle Ages, Albertus Magnus.

Earlier work of Anton van Leeuwenhoek, who invented the first microscopes and saw microscopic organisms, and Francisco Redi who showed that flies laid tiny eggs on decaying meat which gave birth to maggots, first questioned spontaneous generation. But these early skeptics were lambasted, using studies that are now understood as flawed. [There were hundreds of impressive-looking, published studies, and textbooks with long bibliographies, that seemed to support spontaneous generation.] Proponents continued to derive increasingly more complicated explanations to explain each study that failed to support spontaneous generation, arguing, for instance, that heat destroyed a vital life force or that spontaneous generation needed air.

During his lifetime, Dr. Pasteur was the object of intense opposition by virtually the entire scientific community. It was only his persistence and sound experimental and analytical procedures that finally compelled most biological and medical scientists to give up their ideas of the naturalistic origin of life and their treatment of disease based on this notion.

This is a story that is important for today because of the larger lesson he taught mankind: the scientific process. He showed how easy it is, even for scientists, to be misled to believe things that aren’t true without meticulous observations and understanding what makes a sound test of an hypothesis. He illustrated the importance of designing experiments to eliminate confounding factors and bias.

As Seung Yon Rhee, Ph.D., of the department of plant biology at Carnegie Institution of Washington and the principal investigator at the Arabidopsis Information Resource, wrote for the National Health Museum:

Pasteur's achievements seem wildly diverse at first glance, but a more in-depth look at the evolution of his career indicates that there is a logical order to his discoveries. He is revered for possessing the most important qualities of a scientist: the ability to survey all the known data and link the data for all possible hypotheses, the patience and drive to conduct experiments under strictly controlled conditions, and the brilliance to uncover the road to the solution from the results.

On the discipline of rigid and strict experimental tests he commented, “Imagination should give wings to our thoughts but we always need decisive experimental proof, and when the moment comes to draw conclusions and to interpret the gathered observations, imagination must be checked and documented by the factual results of the experiment.”

As she explained, the pattern of logic and brilliance of his experimental method are now well appreciated in modern scientific research, with its series of careful observations, and well-designed experimentations to test each hypothesis in increasingly more detail.

Later in his career, he was approached with a contamination problem in alcoholic fermentation, which was thought to be an entirely chemical process at the time. After careful examination, he found that the fermenting solution contained optically active compounds and concluded that fermentation was a biological process carried out by microorganisms. This hypothesis, called the germ theory, was followed by many elegant experiments that showed unequivocally the existence of microorganisms and their effect on fermentation…

The spontaneous generation theory was considered finally laid to rest in 1859 when the French Academy of Sciences held a contest for the best experiment to prove or disprove the theory. It was Pasteur’s famous experiments that refuted spontaneous generation and convincingly showed that microorganisms are everywhere, even in the air, and can contaminate solutions, but that air itself doesn’t create microbes.

Pasteur first filled flasks with beef broth and boiled the broth, leaving some flasks opened to the air to cool and sealing others. While the sealed flasks remained free of microorganisms, the open flasks were contaminated within a few days. Next, he placed boiled broth in flasks that had open-ended, long necks that he had bent into sharp S-shaped curves. Air could enter the flask, but airborne microorganisms could not — they settled by gravity in the sharp dip in the neck. As he predicted, broth in these uncapped flasks remained uncontaminated even months later. Then, when he tilted the flask so that the sterile broth reached the part of the neck where the airborne microbes had settled, the broth quickly became clouded with teaming life.

It was Pasteur’s simple, but elegant experiments, that struck the “mortal blow” to spontaneous generation. In doing so, he also helped support the understanding of contagious diseases and infections as caused by germs. As Dr. Rhee said:

Pasteur's intuited that if germs were the cause of fermentation, they could just as well be the cause of contagious diseases. This proved to be true for many diseases such as potato blight, silkworm diseases, and anthrax. After studying the characteristics of germs and viruses that caused diseases, he and others found that laboratory manipulations of the infectious agents can be used to immunize people and animals.

Scientific progress was made possible by the scientific process, which is simply a method of critical reasoning. The scientific community came to recognize the merits of the scientific method and it has resulted in the exponential advancement in science and technological discoveries we’ve enjoyed over the past century. As hypotheses fail to be supported in well-designed research, sound scientists move on. Junk scientists don’t, which is why unsound science also never progresses but continues to test the same things, hoping for different results. Incredibly, there are people to this day who reject the germ theory and the scientific process. Sadly, they are unable to recognize sound science from fraud, pseudoscience, ideology and the popularity of beliefs. This leaves people prey to all sorts of unsound things that can needlessly worry or take advantage of them - and it's very hard to help people when science and scientific evidence is rejected.

But even mainstream scientists and doctors can be taken in by flawed observations and statistics, failing to ask the right question, poorly-designed studies that are not fair tests of an hypothesis, and biased interpretations of the evidence. Cognitive disconnect requires constant diligence on everyone's part and to remember to keep our critical thinking caps on.