_Pathology_.--If the foreign body completely obstructs a main bronchus, preventing both aeration and drainage, such rapid destruction of lung tissue follows that extensive pathologic changes may result in a few months, or even in a few weeks, in the case of irritating foreign bodies such as peanut kernels and soft rubber. Very minute, inorganic foreign bodies may become encysted as in anthracosis. Large objects, however, do not become encysted. The object is drawn down by gravity and aspirated into the smallest bronchus it can enter. Later the negative pressure below from absorption of air impacts it still further. Swelling of the bronchial mucosa from irritation plus infection completes the occlusion of the bronchus. Retention of secretions and bacterial decomposition thereof produces first a "drowned lung" (natural passages full of pus); then sloughing or ulceration in the tissues plus the pressure of the pus, causes bronchiectasis; further destruction of the cartilaginous rings results in true abscess formation below the foreign body. The productive inflammation at the site of lodgement of the foreign body results in cicatricial contraction and the formation of a stricture at the top of the cavity, in which the foreign body is usually held. The abscess may extend to the periphery and rupture into the pleural cavity. It may drain intermittently into a bronchus. Certain irritating foreign bodies, such as soft rubber, may produce gangrenous bronchitis and multiple abscesses. For observations on pathology (see Bibliography, 38). _Prognosis_.--If the foreign body be not removed, the resulting chronic sepsis or pulmonary hemorrhage will prove fatal. Removal of the foreign body usually results in complete recovery without further local treatment. Occasionally, secondary dilatation of a bronchial stricture may be required. All cases will need, besides removal of the foreign body, an antituberculous regimen, and offer a good prognosis if this be followed.