One group of rats were fed only meat and another group only bread for several weeks. The two groups were inoculated with the same inoculum at the same time. The meat rats who had become distinctly stronger and heavier were immune while the bread rats, in spite of equal age, without exception succumbed to the anthrax injection.
Trans. of Berliner und Muenchener Tieraerztliche Wochenschrift (Germany), v23, p197-201, 1879.