Once the tuberculosis bacilli are inhaled into the human lungs, if the individual’s resistance is strong, the process of reproduction of the tuberculosis bacilli will be inhibited by the resistance, and usually they will not reproduce in large quantities to cause serious damage, and no tuberculosis will occur, or only very mild tuberculosis will occur; in this type of tuberculosis, some people do not even feel it at all, and when the lungs are examined, they are found to have calcified spots that have healed on their own after the tuberculosis invasion. For people with poor resistance, or people who inhaled a very large amount of TB bacteria at once (if a TB patient is sneezing without turning his head and you happen to face him at a very close distance), the resistance in the body may not be enough to inhibit or kill the multiplication of the invading TB bacteria. In this case, the tuberculosis bacillus rapidly multiplies and grows in the body and invades the lung tissue, causing necrosis of a part of the lung, and the necrotic lung tissue may even form a cavity in the lung after the sputum is coughing out of the body. In other cases, some of the tuberculosis bacteria may enter the damaged blood vessels in the lungs and reach various parts of the body with the blood flow, such as the brain (causing meningitis or brain tuberculoma), bone (causing bone tuberculosis), and kidney (causing kidney tuberculosis).