We all know that when we are down with flu, it is a set of microbes that have invaded our bodies, thereby giving rise to the symptoms. In addition to this, we are also aware that boiling water and heating food items kills the germs, and makes them safe for consumption. It isn’t rocket science, is it?
But way back in the 1800s, it was not this simple. We owe our current understanding of germs or microbes to a French chemist and microbiologist called Louis Pasteur. Apart from his germ theories of fermentation and disease, we also know him as the genius who gave us the process of pasteurization.
Given below is a brief account of the germ theory of disease, as well as the significant experiments and observations of Louis Pasteur, his germ theory of fermentation and its extension to diseases.
What is ‘Germ Theory of Disease’
In the 1800s, this idea was not widely accepted, and it took a series of experiments and hard work for Pasteur to prove that air contains infinitely small living organisms, and that these organisms are responsible for diseases.
Such tiny living things, which we know today as microorganisms, were first observed by Antonie van Leeuwenhoek, way back in the 1670s. Moreover, the presence of microscopic, disease-carrying agents was proposed by several individuals, hundreds of years before the time of Pasteur. Observations and speculation hinting towards the presence of germs and their involvement in disease also came from the works of Fracastorius, Edward Jenner, Ignaz Semmelweis, Agostino Bassi, John Snow, and several more. But the presence of tiny invisible organisms in air was ridiculed and considered to be a fanciful story.
It was only in the 1860s that this proposition was strongly backed by evidence that came from the experiments by Louis Pasteur, followed by pioneering studies by Robert Koch and Joseph Lister. This greatly revolutionized the approach towards the study of infectious diseases as well as the treatment methods.
What paved the way for the Germ Theory of Disease?
Louis Pasteur took two swan-neck flasks containing a rich liquid broth, and boiled the broths. He retained one flask as it is; and broke the neck of the other flask. The broth in the first flask remained as it is; whereas the broth in the second flask became cloudy which indicated microbial growth.
Dust particles in air entered the first flask but were stuck in the swan neck and could not travel into the broth. On the other hand, dust particles easily fell in the second flask, thereby introducing microbes into the broth. This experiment proved the existence of germs in air (dust particles in air, to be precise), and served as the final nail in the coffin of spontaneous generation theory. This experiment silenced all the debates between germ theory and spontaneous generation theory of origin of life.