1. Cysts

Cysts are of extremely rare occurrence in the lungs, which in this respect present a marked contrast with many of the other parenchymatous organs.

Simple Serous Cysts may, doubtless, occasionally be found in the lungs, but sacs containing Acephalocysts are of less rare occurrence. The rarity of the latter cysts in the lungs contrasts strongly with their frequency in the liver, and this is very important when we consider the frequency of pulmonary tuberculosis, for this, in addition to the inverse ratio of the frequency of these secondary products in other organs, especially in the liver, constitutes one of the most important objections to the theory that tubercle has a hydatid origin.

Hitherto only single sacs of acephalocysts appear to have been found in the pulmonary tissue; they have varied from the size of a pigeon's egg to that of a man's fist, and have occurred sometimes in the upper and sometimes in the lower lobes.

They are undoubtedly developed in the interstitial tissue of the lungs, and occasion, according to their size, more or less compression of the parenchyma, which is thus gradually converted into fibro-cellular tissue (obsolescence). The parent sac is surrounded by and adherent to this tissue, and contains, in its interior, the acephalocysts, which vary in number and form, and either swim freely in a serous fluid or are attached to the walls.

It is important to recollect that in rare cases the parent sac may be destroyed by inflammation and consequent suppuration, and a communication may thus be established between the cavity and the bronchi, through which the acephalocysts may be ejected, especially as in less rare instances acephalocysts are ejected from the liver by this complicated route.

The pulmonary sac containing acephalocysts often communicates with a similar sac in the liver.

Cysts containing other substances, as for instance cholesterin, with or without hair, are even rarer than cysts with serous contents.

2. Anomalous Fibrous Or Fibrocartilaginous Tissue

Anomalous Fibrous Or Fibrocartilaginous Tissue occurs a. As callous condensation arising from chronic inflammation of the interstitial tissue; it likewise occurs as cicatrix-callus around old abscesses, tuberculous cavities, apoplectic effusions, etc.

b. Fibroid Tumors are incomparably rarer. They never attain any considerable size, being seldom larger than a bean or a hazel-nut. They are either bluish-white, firm, elastic, very dense and flat bodies, or, as is more frequently the case, they are of a pale yellow or dirty white color, flabby, soft, and puckered, and resemble the structure of the mammary or salivary glands.

3. Anomalous Osseous Substance

Anomalous Osseous Substance occurs not only in the bronchi (see p. 35) and bronchial glands, but under various circumstances, in the lungs, especially in the form of ossification of anomalous fibrous tissue or of the chalky metamorphosis of an unorganized structure. To the first belong many either flat or roundish and nodular, yellow, and generally very compact concretions, which are developed in and from all the forms of anomalous fibrous tissue, but especially in the callous stripes, capsules and cicatrices; to the latter belong the chalky, whitish or grayish nodular, brittle, and even friable masses into which tubercle and tuberculous pus are, under certain conditions, metamorphosed.

4. Black Figment

Black Figment is more frequently and abundantly deposited in the lungs and bronchial glands than in any other organ, except the mucous membrane of the intestinal tract. It occurs, with rare exceptions, in the lungs of all adults, and increases with advancing years. Hence it can properly be only regarded as a pathological appearance, either when it occurs in the earlier periods of life or in excessive quantity.

The pigment which occurs in the form of molecules is either deposited in a, free state in the interstitial tissue and in the walls of the air-cells, or else it is combined, as a new formation, with some older deposit.

In the first case it is found according to the extent of the accumulation, in blackish-gray, blackish-blue, or ink-black points, or in patches, as if laid on with a brush; or if very abundantly present, it is diffused over the interstitial tissue in large ramifying streaks, which appear as islands in the cellular tissue under the pulmonary pleura, and are uniformly infiltrated, blackened, and as it were inked, and are thickened and tough. This thickening of the interstitial cellular tissue is important, since it impedes the development of the air-cells, and likewise gradually obliterates their vessels, and in this manner causes their atrophy. We must here especially notice a metamorphosis which not unfrequently occurs at the apices of the upper lobes, and is unassociated with any other anomaly; we refer to the deposition of large quantities of pigment which give a black color to the tissue, and increase its firmness, its structure being either normal or presenting at some spots an irregular reticulated appearance in consequence of atrophy. Senile atrophy of the lungs is undoubtedly often induced by an excessive accumulation of pigment in the interstitial tissue. The deposit usually takes place through the whole lung, but is most abundant near the surface and in the upper third of the superior lobes. It is the result of slight irritative processes and of transient stases; the pigment is conveyed by absorption to the bronchial glands, and is thus deposited in them. It must be decided by further and more careful observations whether the larger deposits of pigment which are so frequently noticed in the lungs of persons engaged in working both coal and coal dust, depend upon the actual absorption of these extraneous matters into the tissue, or whether, as we are more inclined to believe, they are the results of the continued irritation to which the pulmonary mucous membrane of such persons is necessarily subjected.

In the second case the pigment is the result of a chronic pneumonia, and we find it infiltrated in various quantities into an indurated and callous parenchyma. We meet with it in the vicinity of tuberculous deposits, especially of hemorrhagic tubercle, and in certain cancerous deposits, especially in cancer melanodes.