Louis Pasteur in his experiment boiled an organic fluid (called Bouillon) in a special type of flask with a long S-Shaped tube, whose neck was sealed. The nutritive material remained sterile in the flask so that no micro-organism could enter into the flask. When he opened the flask, the micro-organisms from the air immediately entered into the flask and started reproducing in the broth. The S-shaped tube did not permit the entry of the micro-organisms into the flask, immediately.
When the S-shaped tube was broken off, near the neck of the flask, microbes at once, entered the flask and propagated in the broth. Pasteur reasoned that microorganisms had entered the flask from the atmosphere. But in the first case, when the long S-shaped tube was intact, they failed to reach the broth, as they got trapped on the walls of the tube. By boiling the broth, he had made the medium sterile (free of micro-organisms) and micro-organisms from the atmosphere were prevented from entering the flask by the S-shaped tube. With this experiment, he proved that selfgeneration of an organism is impossible.
