Final answer:
Louis Pasteur is credited with definitively refuting the theory of spontaneous generation using his swan-neck flask experiment, which demonstrated that microorganisms from the air are responsible for contamination, not a 'life force' as previously thought.
Step-by-step explanation:
Louis Pasteur and the Refutation of Spontaneous Generation
The individual credited with definitively refuting the theory of spontaneous generation using broth in swan-neck flasks is Louis Pasteur. His groundbreaking experiments conducted in the mid-19th century conclusively demonstrated that microorganisms are present in the air and can contaminate broth, leading to the appearance of life. Before Pasteur, other scientists like Francesco Redi, John Needham, and Lazzaro Spallanzani had conducted various experiments that fueled the debate. However, it was Pasteur's swan-neck flask experiment that delivered the final blow to the theory of spontaneous generation. By boiling broth in a flask with a swan-neck-shaped tube, Pasteur was able to show that when the neck remained intact, no microbial growth occurred, disproving the idea that life could spontaneously arise from nonliving matter.
Pasteur's experimental design allowed air to enter the flask but prevented the entry of bacteria and fungal spores due to the trap formed by the swan neck. This was crucial in demonstrating that the microorganisms that contaminated the broth came from the air, and not from within the broth itself or from some mystical 'life force'. Pasteur's work was well-received and awarded, cementing his legacy in the sciences.