Pasteurs Experiment

By the mid-1800s, the controversy over spontaneous generation had grown fierce. The Paris Academy of Science offered a prize to anyone who could clear up the issue once and for all. The winner of the prize was the French scientist Louis Pasteur (1822-1895).

Figure 14-3 shows how Pasteur set up his prize-winning experiment. To answer objections to Spallanzani's experiment, Pasteur made a curve-necked flask that allowed the air inside the flask to mix with air outside the flask. The curve in the neck of the flask prevented solid particles, such as microorganisms, from entering the body of the flask. Broth boiled inside the experimental curve-necked flasks remained clear for up to a year. But when Pasteur broke off the curved necks, the broth became cloudy and contaminated with microorganisms within a day. Pasteur reasoned that the contamination was due to microorganisms in the air.

Those who had believed in the spontaneous generation of microorganisms gave up their fight. With Pasteur's experiment, the principle of biogenesis became a cornerstone of biology.

Curved neck is removed.

figure 14-3

Broth becomes cloudy.

In Pasteur's experiment, a flask with a curved but open neck prevented microorganisms from entering. Broth boiled in the flasks became contaminated by microorganisms only when the curved necks were removed from the flasks.

Word Roots and Origins biogenesis from the Greek bioun, meaning "to live," and gignesthai, meaning "to be born"

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