This may be either congenital, the lungs being involved as well as other parts of the body, or it may be acquired.

The congenital is the more common and occurs as white pneumonia, a diffuse form resembling bronchopneumonia. The lungs are whitish in color, completely airless, and firm. Microscopically there is a desquamation of the alveolar epithelium, an infiltration of leukocytes, and a connective-tissue proliferation in the interalveolar and interlobular tissues. There is usually some proliferation of the adventitia of the blood-vessels, also of the intima, so that some of the vessels may be completely obliterated.

Gummata may be present in the new-born either alone or associated with diffuse lesions; are sometimes found in adults. They generally occur near the root of the lung, beneath the pleura, and are commonly few in number and more or less circumscribed. They undergo the usual cycle of round-cell infiltration, connective-tissue proliferation, coagulation necrosis, and, in case of recovery, organization. They frequently undergo caseation, and it may be very difficult, if not impossible, to distinguish them from tuberculosis, except by staining for the tubercle bacillus. These areas present the ordinary microscopic appearances of gummata. The blood-vessels, besides showing a thickening and hyaline degeneration, are surrounded by a round-cell infiltration. The caseous material may be expectorated and the cavity be obliterated by the formation of a cicatrix.


This is very rarely found in the lung in man. The Bacillus mallei may gain entrance by inhalation or by the blood, following infection of the skin. In the first form numerous grayish or yellowish nodules, varying in size up to that of a pea, are found scattered throughout the lobes. They are made up of a mass of round cells and frequently undergo caseous degeneration.

When infection takes place by the blood there is a diffuse purulent infiltration of large areas of lung, with the formation of abscesses and associated hemorrhagic infiltration.


Seldom occurs. It may result from aspiration of the infecting organism, but is more often a secondary condition following actinomycosis of the upper air-passages or of the anterior or posterior mediastinum. There may be a single focus of infection in the form of a cavity containing a thick cheesy and purulent material in which the characteristic yellowish actinomyces granules are present. Numerous communicating cavities may be present. The lesions may be more general and nodular, these nodes tending to undergo central softening. On account of proliferation of the surrounding connective tissue they may closely resemble tubercles.


Primary growths in the lungs are unusual; secondary ones somewhat more common. Of the connective-tissue variety, small fibromata, lipomata, chondromata, and osteomata are found. Primary sarcoma is more common than the above and probably originates within the peribronchial lymph-nodes as a small round-cell or spindle-cell tumor. May have primary endotheliomata of the pleura with extension into the lung.

Secondary sarcoma of the lung is very common. It occurs in nearly every case of primary sarcoma elsewhere. Numerous small scattered nodules are found. These are whitish in color and frequently undergo softening.

Primary carcinoma is very rare, but it may develop from the mucous glands of the bronchi or a squamous epithelioma from the epithelium of the terminal bronchi and alveoli.

Secondary carcinoma is not as common as secondary sarcoma. It results from emboli of tumor cells lodging in the capillaries. May follow extension of an esophageal or mammary carcinoma. Sometimes may have secondary growths resulting from the inspiration of cellular particles of a carcinoma of the mouth or upper air-passages. Such cases may be associated with areas of bronchopneumonia.

Adenomata have been met with and dermoid cysts occasionally appear.

In leukemia numerous miliary growths consisting of small round cells may be found. They resemble tubercles except that they are somewhat whiter and softer, but do not tend to undergo caseous changes.


Besides the specific organisms mentioned various vegetable parasites, as the aspergillus, the mucor, and the o´dium, may be met. Are found at times in tuberculous cavities. May give rise to a pneumonomycosts aspergillana.

Animal parasites such as the lung fluke are sometimes found. It gains lodgment near the root of the bronchi and discharges its eggs into the mucopurulent secretion that it excites. The eggs are found in the sputum. May give rise to hemoptysis. The cysticercus cellulosoe, the strongylus longi-vaginatus, monas, cercomonas, coccidia, and psorosperms, may all be occasionally found in the lung.

The most important is the echinococcus. It is usually secondary to primary disease of the liver and is most common in the lower right lobe. There are one or more cysts which may vary greatly in size. As a rule, the cyst occasions no symptoms, becoming inspissated and calcified. Sometimes it ruptures into a bronchus; in such a case the cystic contents will be expectorated and in the sputum characteristic hooklets can be found. An empyema can be caused by the cyst rupturing into the pleural cavity.