What did spallanzani do to improve upon redis and needhams work?

Spallanzani improved upon Redi and Needham's work by conducting more controlled experiments and providing stronger evidence to support the theory of biogenesis. Here are some key points regarding Spallanzani's contributions:

1. Sealed Flask Experiment:

- Spallanzani conducted experiments using sealed flasks containing boiled broth, which he then heated to kill any existing microorganisms.

- He sealed the flasks to prevent air from entering and left some open to the air as controls.

- After several days, he observed that the sealed flasks remained free of microorganisms, while the open flasks showed signs of microbial growth.

2. Extended Boiling:

- Spallanzani extended the boiling time of the broth to ensure complete sterilization.

- He boiled the broth for longer periods compared to Needham, who used shorter boiling times.

3. Use of Control Groups:

- Spallanzani included control groups in his experiments, which were open flasks exposed to air.

- This allowed him to compare the results between sealed and open flasks and demonstrate that microbial growth occurred only in the open flasks exposed to air.

4. Microscopic Observations:

- Spallanzani used microscopes to observe microorganisms and their behavior.

- He provided detailed descriptions and illustrations of various microbial forms, supporting the idea that microorganisms were living organisms.

5. Response to Needham's Counterarguments:

- Spallanzani addressed Needham's counterarguments, such as the claim that air itself contained a "vegetative force" capable of generating life.

- He conducted experiments where he filtered the air entering sealed flasks and showed that filtered air did not lead to microbial growth.

6. Disproving Spontaneous Generation in Organic Matter:

- Spallanzani also investigated spontaneous generation in organic matter other than broth.

- He heated infusions of hay and other plant material in sealed flasks and observed the absence of microbial growth.

7. Criticism and Impact:

- Despite Spallanzani's thorough experiments, his work still faced criticism from some contemporaries who remained skeptical of biogenesis.

- However, his contributions were significant in strengthening the case against spontaneous generation and paving the way for further advancements in microbiology.

By conducting rigorous experiments, utilizing control groups, addressing counterarguments, and providing microscopic observations, Spallanzani made substantial improvements to the work of Redi and Needham. His contributions played a crucial role in discrediting the theory of spontaneous generation and supporting the principle of biogenesis, which states that living organisms can only arise from pre-existing living organisms.