experiment by louis pasteur
Louis Pasteur was the scientist who disapproved the theory of spontaneous generation by his swan neck flask experiment. His
experiment was as follows:
1) He took two flasks and added nutrient rich broth to both of them. He then bent the neck of the flask into S-shape and boiled the broth to kill the existing microorganism in it.
2) After sterilizing the broth, he broke the swan neck of one of the flask exposing the nutrient rich broth present in it with the air while the second flask was left as it is.
3) After some time, the dust particles fell down inside the broken flask while the dust particles got accumulated near the tip of the swan neck of the second flask. Due to gravity, the dust could not travel upwards along the swan neck, thus keeping the nutrient rich broth free from dust.
4)He found that the nutrient broth inside the broken flask became cloudy while the broth inside the swan neck flask remained clear.
The cloudy effect in the broken flask concluded the presence of microorganisms. Thus Louis Pasteur concluded that no life can arise without the presence of dust which is necessary for carrying the microorganisms. Therefore by this experiment, he refuted the theory of spontaneous generation which stated that life can originate spontaneously from non living matter.
Louis Pasteur in his experiment boiled some broth in flasks having bent swan or S-shaped neks. No microorganisms were observed or found in broth after keeping for several days though broth was connected to air through the bent neck .It is because the dirt carrying microorganisms got setteled in the bent part of the neck. When the neck was broken, colonies of microorganisms soon developed over the broth showing that microorganism s have come from air.