Microbiology 9th Edition by Laura Black, Jacquelyn Black

Exercise 31

Use the following diagram to explain how Pasteur's swan necked flasks prevent contamination of sterile broth the flasks. Describe what happens to the sterile broth (a) after it has been allowed to cool as in (b). What happens to the broth after the flask has been tipped enough to let the broth come in contact with the dust and microorganisms and is tipped back as in (c)?