In Paris, in 1859, Louis Pasteur took Redi’s experiments further. He placed boiled meat broth in a swan-neck bottle, a round flask with a vertical neck bent into an S shape, like a swan’s neck. When Pasteur left the swan-neck bottle open to the air, the broth remained sterile: microbes in the air could not easily travel through the curve in the neck. But when he tipped the flask to expose the broth to the air, or cracked the swan neck, the broth grew out a turbid culture of microbes. Bacterial cells, Pasteur concluded, are carried in air and dust. Putrefaction, or rotting, was not caused by
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