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