Final answer:
The swan neck flask was used by Louis Pasteur to disprove the theory of spontaneous generation by showing that microbial growth in broth was due to airborne microorganisms, which were trapped by the flask's design while still allowing air to pass through.
Step-by-step explanation:
Purpose of the Swan Neck Flask
The purpose of the swan neck flask, designed by French scientist Louis Pasteur, was to demonstrate that microbial growth in broth was due to airborne microorganisms and not a spontaneous generation. The flask had a long, curved neck that allowed air to pass through while preventing microorganisms from reaching the broth. The swan neck effectively trapped bacteria and other particles, thus proving that microbes present in the air were responsible for contamination. When the sterilized broth was left undisturbed in the flask with the intact swan neck, it remained sterile, showing that microbial growth did not occur without the introduction of microorganisms.
According to Pasteur, if microorganisms were not the cause of fermentation and putrefaction, the life force should still have been able to access the broth, even without the microorganisms, but this was not the case. This experiment was crucial for finally refuting the theory of spontaneous generation, a belief that living organisms could arise from non-living matter.