It is the same principle applied to detecting land mines, only the rats are trained to recognize the scent of specific molecules that reflect the presence of the tuberculosis germ—not the explosive vapor associated with land mines.To keep the animals motivated, positive samples are mixed in with the unknown samples. When the rat alerts by scratching at a known sample, a buzzer is sounded and the rat is rewarded with a treat.Any suspect samples are triple-checked, and if found to be positive, they're reported back to the clinics.