Louis Pasteur designed swan-necked flasks to:

• A. Keep maggots away from decaying meat.
• B. Pasteurize beer and wine.
• C. Trap microorganisms from the air in the neck of the flask.
• D. Allow dust to reach sterile infusions.

Answer: (C)

Verified step by step guidance

1. Understand the historical context: Louis Pasteur was a pioneering microbiologist who conducted experiments to disprove the theory of spontaneous generation, which suggested that life could arise from non-living matter.
2. Recognize the purpose of the swan-necked flask: Pasteur designed these flasks to allow air to enter while preventing microorganisms from contaminating the broth inside. The unique shape of the neck traps airborne particles, including microorganisms, in the bend, preventing them from reaching the sterile liquid.
3. Identify the experimental setup: Pasteur boiled the broth in the flask to sterilize it, killing any existing microorganisms. The swan-necked design allowed air to enter but trapped dust and microorganisms in the neck, keeping the broth sterile.
4. Analyze the outcome of the experiment: If the neck of the flask remained intact, the broth stayed clear and free of microbial growth, demonstrating that microorganisms did not spontaneously generate in the broth. If the neck was broken, microorganisms could enter, and the broth would become cloudy due to microbial growth.
5. Conclude the significance: Pasteur's experiment provided strong evidence against spontaneous generation and supported the germ theory of disease, which states that microorganisms are the cause of many diseases.