This is seated in the bronchial mucous membrane, which becomes so infiltrated with yellow, lardaceous caseous, tuberculous matter, as finally it appears converted into it. The bronchial tube itself becomes considerably enlarged, its calibre becoming at length completely obstructed by tuberculous matter, while its fibrous sheath becomes infiltrated with lardaceous matter, callous, and thickened. This degeneration sometimes attacks the bronchial mucous membrane as a secondary affection, in which case it arises from tuberculous abscesses, and affects the tubes opening into them; it is then primarily dependent on pulmonary phthisis.

Primary bronchial tuberculosis is a much more important affection. It is, as we have already mentioned, a disease of the ultimate ramifications of the bronchial tubes, arising originally in them, and extending backwards to the larger bronchi. Like pulmonary tuberculosis, it most commonly occurs in the bronchial ramifications of the upper lobes, but it stands contrasted with that affection in frequently occurring in the peripheral branches; it attacks a large portion of the bronchial tree, and on making a section of the pulmonary parenchyma we find it traversed by thick-walled, dilated, bronchial tubes, filled with caseous tuberculous matter.

Bronchial tuberculosis, although very frequently combined with lar-daceo-gelatinous, or fatty and caseous tuberculous infiltration of the lungs, sometimes occurs as an independent disease. In the latter case the obstruction in the bronchial tubes gives rise to obliteration of the pulmonary vesicles and obsolescence of the parenchyma connected with them; and, on making an incision, we then find the obstructed tuberculous bronchi ramifying through the parenchyma in the form of ribands of puckered, tough, elastic tissue.

The tuberculous matter may undergo either of the two following changes. It may soften; and in this way it not unfrequently destroys the bronchial walls, and gives rise to tuberculous abscesses in the adjacent parenchyma. The abscesses arising primarily from the destruction of the bronchus are incomparably rarer than those arising from the softening of pulmonary tubercles. This metamorphosis is most likely to occur when tuberculous infiltration of the parenchyma is simultaneously present. The other change to which we referred is the cretefaction of the tuberculous matter. This metamorphosis most commonly occurs when the bronchial tube has been completely obstructed by tuberculous matter, and the pulmonary tissue to which it pertains has become obsolete; under favorable conditions it seems, however, sometimes to occur in other cases, in which the morbid product becomes as it were disintegrated into a caseous pultaceous mass, which, instead of becoming softer thickens and becomes ultimately converted into a chalky substance, around which the bronchial tube becomes contracted and atrophied.

Bronchial tuberculosis, as a primary affection, is most common in childhood, and is usually associated with all the tuberculoses of other organs peculiar to this period of life, and especially with intense tuberculosis of the bronchial glands.

Its most marked analogies are exhibited in tuberculoses of the mucous membrane of the Fallopian tubes and uterus.