When he inoculated healthy chickens with weakened cultures of the cholera microbes, the chickens suffered only a mild sickness and were thereafter immune to the disease. Pasteur successfully applied this technique of immunization to the prevention of anthrax. Many scientists challenged Pasteur's anthrax prevention claims, and Pasteur agreed to a dramatic test. Forty-eight sheep and a few cows and goats were gathered in a pasture near the town of Melun. The test verified Pasteur's results beyond all doubt.
Rabies slowly destroys the central nervous system by attacking the spinal cord.
Pasteur reasoned that it might be possible to immunize people after they had been bitten but before destruction of the spinal cord began. He took spinal cord tissues of animals that had died of rabies and dried them for varying periods of time. He then made inoculations of the tissues and injected them into another stricken animal. The first inoculation was from the driest, weakest culture, and each successive inoculation was stronger. After repeated failures, he finally succeeded in halting the development of rabies in an infected dog.