What was the outcome of Florey and Chain's experiments with mice in 1940?

Florey and Chain's experiments with mice in 1940 were pivotal in demonstrating the potential of penicillin as an effective antibiotic. When they administered penicillin to a group of infected mice, they found that a significant number of the treated mice survived the lethal infection compared to those that did not receive the drug. Specifically, it was observed that about half of the injected mice survived, showcasing the drug's powerful effects against bacterial infections. This experiment was crucial as it set the foundation for further research and eventual widespread use of penicillin in medicine, highlighting how it could save lives during bacterial infections.

The other options relate to incorrect outcomes or focus on unrelated advances. There were no new surgical methods developed from this experiment, nor was a new vaccine for typhoid created in this context. The idea that all mice survived is also inaccurate, as the results demonstrated only partial success. This makes the correct choice about the survival of half of the injected mice the most accurate reflection of Florey and Chain's findings.