Which S-shaped lab vessel did Pasteur use in experiments against spontaneous generation?

Pasteur used a swan-neck flask—a round-bottom vessel with a long, curved S-shaped neck—in experiments against spontaneous generation. The bend allowed air to enter while trapping dust and microbes before they reached the boiled broth.

In Pasteur’s demonstrations, nutrient broth was heated to kill existing organisms. The liquid remained clear when the flask stayed upright, even though its opening was exposed to air. When the flask was tilted so the broth touched contaminated material collected in the neck, microbial growth appeared.

This design helped show that organisms in the broth came from contamination carried by particles, not from the broth spontaneously producing life. The experiments supported biogenesis and became part of the historical foundation of germ theory.

The vessel is sometimes called a gooseneck flask, but “swan-neck flask” is the standard quiz answer. An Erlenmeyer flask is also a laboratory vessel, but its conical shape does not provide the distinctive curved trap used in Pasteur’s experiment.