How did Robert Koch demonstrate that the tuberculosis bacillus caused disease in animals?

To demonstrate that the tubercle bacillus was the cause of tuberculosis, Robert Koch first identified the organism in the tissues of infected humans and animals using modified staining techniques.1

Because the bacillus was initially difficult to grow, Koch overcame this challenge by successfully isolating the organism in a succession of pure culture media. He then established the bacterium's etiologic role by inoculating healthy animals with these cultures, which subsequently induced the disease. This rigorous process allowed him to confirm his hypothesis and announce his findings to the Physiological Society of Berlin in 1882.1