Louis Pasteur and his Germ Theory


The average life expectancy around 1CE, when Jesus was born was a mere 20 years. As we move forward on the time axis, life expectancy also progressed slowly. In the 1800s, the time when Charles Darwin and Abraham Lincoln were born, it reached about 26 years. During the latter half of the 19the century, it reached about 29 years.

On average, a child born today is expected to live about 70 years. Of course, this varies from country to country, but on average, the life expectancy of the world in 2019 is over two-thirds of a century. How did this happen? Why the people did live a much shorter life about two millennia ago?

The answer to this question is centered on a French Man, Louis Pasteur. He was one of the world’s foremost experts on germs and made some remarkable discoveries about germs and their role in spreading diseases. He played an instrumental role in developing some of the earliest methods to tackle these germs and make humans healthy again.

In 1856, Louis Pasteur was commissioned by an alcohol manufacturer to determine the cause that was turning beetroot alcohol to sour. “There’s a fine line between wine and vinegar.” This is what he discovered.

During that time, most of the scientists around the globe were convinced that fermentation was purely a chemical process which doesn’t involve any ‘living being’. However, Pasteur’s work on fermentation led him to conclude that it was yeast, a living organism which turned beet into alcohol. When he observed this yeast under a microscope, he found them to be round and plump. But when he observed the spoiled alcohol under the microscope, he found that it contained a different bacterial which was rod-shaped. He speculated that this bacterium is Mycoderma aceti, which is commonly used to make vinegar, which spoiled the wine.

Now, the question arose, how did yeast reach wine? To understand this, he decided to study the fermentation of broth over time. He placed the flasks with broth with filters (to keep the dust particles away, which would have entered otherwise into the flask). When he opens the flasks, he noticed that no fermentation took place in flasks indicating that it was something outside the broth which came in along dusty air and caused the fermentation of broth. Hence, he concluded that there were “germs” that came along the air, which he believed were responsible for causing the biological changes in food and beverages. This was called the Louis Pasteur’s germ theory of fermentation.

Years later, extending this idea, he wondered that if external air and particles that were responsible for spoiling food and beverage were also likely to be the external agents or germs that were responsible for ‘infecting’ human bodies. During the advent of the nineteenth century, this germ theory of disease by Pasteur became widely accepted. Eventually, he went on to develop the vaccines for, anthrax, chicken cholera and rabies.

Therefore, it is because of the study of germs and diseases they cause, humans found their way to extend their lives by about three times.



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