In both of the forms already described it has been shown that the tuberculosis, beginning in the finer bronchi, extends, on the one hand, to the lung alveoli, and, on the other, to the connective tissue. Besides that, however, there are further extensions both in the lung and beyond it.

An existing cavity, especially one arising from disintegration of caseous matter, is a great source of infection, its contents being charged with tubercle bacilli. The infected matter is carried from the cavities and is partly insufflated into other parts of the lungs and partly discharged. It thus causes an extension of the disease in the lung itself, and is liable to infect the air passages as it is carried along.

Hence, Tuberculosis of the bronchi is very frequent in connection with cavities, the mucous membrane becoming the seat of tubercular ulcers. If the bronchial tubes be opened up, the ulcers are visible as more or less rounded erosions, sometimes with distinct white tubercles at their borders.

A further extension to the Larynx and Trachea is.very common, and from these, by way of the oesophagus and stomach to the Intestine.

There is also an extension by the lymphatics, so that in nearly all cases of phthisis the Bronchial lymphatic glands are affected. The condition here is similar in character to that in the lungs. In the caseous form the glands are caseous, resembling closely the appearances in ordinary scrofulous glands. In the fibroid form they are liable to be more or less fibrous and deeply pigmented. Tubercles are present in the glands, sometimes in the most typical form. It is not common for softening to occur in the bronchial glands; the tuberculosis is usually chronic in character and the affected glands may ultimately shrink and become calcified. Cretaceous matter is often met with at the roots of the lungs, being the remains of obsolete tuberculous glands.