Tubercles may exist as fine points, not larger than a pin’s head, (_miliary tubercle_,) or the matter may accumulate in masses of the size of a kernel of corn, of a cherry, or of a robin’s egg. In other cases, the pulmonic exudation in some portion of the lung attending an attack of pneumonia, may become transformed into tubercular matter, having an irregular outline and no distinct boundary, (_infiltrated tubercle_.) Tubercular matter is undoubtedly, in most instances, deposited within the air cells, so filling these, as to more or less interfere with the admission of the air, and giving greater density to the portion of lung involved. While the secreted matter is at first soft, or semi-fluid and partially translucent, it gradually acquires greater density, becomes opaque and cheesy in its character, and in all respects acting as a foreign body within the lungs. Sooner or later, the presence of tubercles will excite inflammation in the surrounding tissues. In this manner these bodies may become softened and their substance expectorated. If large numbers be aggregated together, the ulcerative process may completely destroy the tissues between, an abscess or vomica resulting. In the early stage of the disease, before the inflammatory and ulcerative processes have been set up, the presence of tubercular matter, by interfering with the capillary circulation, may give rise to a hæmorrhage into the bronchial tubes, constituting the hæmoptysis so frequently present in this disease; while at a later period, from a destruction of some of the larger vessels from ulceration, a profuse and even fatal hæmorrhage may result. Post-mortem Appearances. In examining the lungs of those who have died after suffering the usual symptoms of pulmonary consumption, we shall find the upper portion of one or both lungs, more or less indurated, and occupied by one or more irregular shaped cavities, containing either air, or air and a quantity of viscid, puriform, dirty-looking fluid. Generally the apex of the affected lung, will be found firmly attached to the inner surface of the chest, by means of a thick, firm, false membrane, which unites the two layers of the pleura. In some instances, nearly or quite the whole surface of the lung will be found thus adhered, while the lobes will also be united by an interlobular false membrane. When the adhesions are confined to the upper portions of the lungs, the pleura covering the lower portion will frequently be found more or less rough from albuminous exudation, while a quantity of sero-purulent fluid will be found in the posterior part of the thoracic cavity.