Needham boiled the broth to kill any existing microorganisms, whereas Lazzaro Spallanzani did not boil the broth.

Spallanzani also boiled broth, but he boiled it for a shorter period than Needham.

Spallanzani also boiled broth, but he did not seal the flask.

Spallanzani boiled broth for a longer period and sealed the flasks more effectively, preventing contamination from the air.