In his famous experiment, Louis Pasteur used a special flask whose neck was shaped like an S or the neck of a swan, hence the name "Swan Neck Flask." He put a nutrient rich broth in the flask, which he called the "infusion." He then boiled the infusion killing any microorganisms which were already present. Then he allowed the infusion to sit.
Because of the shape of the flask, the infusion was exposed to air. However, dust particles and other things in the air never made it into the infusion. Because they were trapped in the curve of the Swan Neck Flask. No matter how long he allowed the flask to sit, microorganisms never appeared in the infusion. However, if he tipped the flask and allowed the things trapped in the neck to get into the infusion then microorgranisms began to appear in the infusion and multiply rapidly. This demonstrates that microorganisms do not appear as a result of Spontaneous Generation. Instead, they are introduced into food through dust particles and other things that happen to land on the food.
Where do cells come from? If a cut of meat is let out, over time it will putrefy and begin to teem with microorganisms and possibly with larger organisms like maggots. Prior to the mid-to-late 19th century, the origin of microorganisms in decaying matter was in question. Some maintained that microbes arose from other microbes that landed on the food from the air. Other supported the hypothesis of spontaneous generation, which states that living organisms can arise spontaneously from nonliving matter.
This simple Louis Pasteur experiment is perfect for teaching kids the basics of microbiology. The steps of his experiment are as follows:
Louis Pasteur designed an experiment to test whether sterile nutrient broth could spontaneously generate microbial life. To do this, he set up two experiments. In both, Pasteur added nutrient broth to flasks, bent the necks of the flasks into S shapes, and then boiled the broth to kill any existing microbes.
After the broth had been sterilized, Pasteur broke off the swan necks from the flasks in Experiment 1, exposing the nutrient broth within them to air from above. The flasks in Experiment 2 were left alone.
Over time, dust particles from the air fell into the broken flasks of Experiment 1. In Experiment 2, dust particles remained near the tip of the swan necks, but could not travel against gravity into the flasks, keeping the nutrient broth sterile.
The broth in the broken flasks quickly became cloudy--a sign that it teemed with microbial life. However, the broth in the unbroken flasks remained clear. Without the introduction of dust--on which microbes can travel--no life arose. Thus, the Louis Pasteur experiment refuted the notion of spontaneous generation.
--- Note from the Pasteur Brewing Editor: The “forcing process” was designed to estimate the relative keeping quality of beers, by investigating the production of healthy yeast and/or bacteria in beer samples, prior to bottling. This is a highly technical process and requires efficient laboratory equipment. ---
We have already in Chapters III and IV made frequent reference to Pasteur's classical researches into the fermentation of Beer and Wine, and we now wish to explain how the methods first employed in those researches, may with advantage be practically applied by the scientific brewer to the regular examination of his product.
Louis Pasteur's experiments fueled his scientific work and validating his ideas with careful experimention was his passion. The most famous Louis Pasteur experiment was that which he created to disprove the theory of Sponteneous Generation, the theory that living organisms can be "spontaneously generated" from non-living material. Through his experimentation Louis Pasteur concluded that microscopic organisms are present in the atmosphere. Therefore, any substance or material exposed to the air would be potentially subject to living processes. He created a special "swan neck flask" for this ground breaking experiment.
Purpose
To allow you to participate in some historically important issues in science, to conduct experiments, and to reason from the data while experiencing the limitations of the data in reaching valid conclusions.
Louis Pasteur was more than just a man; in the words of his latest biographer he was "a living symbol, embodying both science and France." Written for the centenary of Pasteur's death, this book is a comprehensive, insightful examination of his life and work, made far more interesting and accessible by the author's natural flair for describing the details of scientific research with simple, compelling prose.
Louis Pasteur "Real Scientists Drink Beer" Coasters
Pasteur Biography
Louis Pasteur was a microbiologist and chemist from Dole, France. Learn more about his childhood, history at the university and his ground-breaking work that led to the development of modern medicine. We owe the creation of vaccinations, pasteurization and many more applications of science to Louis Pasteur.
Experiments
