Cancer occurs in the lungs both in the form of carcinoma medullare and carcinoma fasciculatum, seu hyalinum. The latter is extremely rare, but the former is comparatively common, and it is to it that the following observations apply.

a. It most commonly occurs in the form of roundish, separate masses, varying from the size of a hemp-seed to that of the fist, and occasionally being even larger, and enclosed in a very delicate cellular capsule; they are composed of gelatino-lardaceous or lardaceo-encephaloid or true en-cephaloid parenchyma, and hence they vary considerably in consistence; they are usually white, but are sometimes of a grayish-red, or dirty yellowish-gray color. They are generally scattered in very considerable numbers throughout the lungs, both near the surface and deep in the texture, and when they are contiguous to the pulmonary pleura, they undergo a flattening or depression. The injury of the surrounding parenchyma is limited to its being displaced and compressed in the immediate vicinity of the adventitious product. It is only very seldom that it undergoes ichorous disorganization, in which case the accumulated cancerous ichor makes its escape by communicating with the bronchi.

It usually proves fatal by the exhaustion induced by its excessive growth, and by the high degree of general cancerous cachexia from which the growth originates. Pulmonary oedema and hydrothorax commonly supervene, either with or without simultaneous cancer of the pleura.

It very rarely occurs in the lungs as primary cancer, that is to say, as the first in a series of successive local cancers; it almost always exists in association with other, and generally many cancerous deposits of older date, distributed over several organs; and is, often developed with great rapidity after the extirpation of large cancers. It is chiefly combined with cancer of the pleura, with which it is usually simultaneously developed, or with cancer of the mediastinum, or of the mammary gland, the liver, the kidneys, or the osseous system.

b. The occurrence of pulmonary cancer as a special form of tubercle is very rare, and is never met with unless when there is cancer in some other organ. It presents itself in the form of tubercles or nodules of the size of a millet or hemp-seed, which, as far as we yet know, may be distinguished from other tubercles by their bluish white color, their softer consistence, their aggregation in groups, and a difference in their elementary structure and composition. They sometimes exist in association with a retrograde genuine pulmonary tuberculosis.

c. Cancerous matter is very rarely infiltrated or effused into the air-cells. When it occurs in this form it is the product of a pneumonic process, which, under the influence of a dyscrasis excited by the extirpation of cancer, assumes the external characters, and the elementary structure of carcinoma; the lung in this case appears hepatized with cancerous matter.

Medullary cancer of the lungs is sometimes more or less blackened by a pigment which enters into its composition; the medullary nodules are marked with brown, blackish-blue, violet, or black spots or stripes, or are completely and thoroughly black, constituting melanotic cancer - cancer melanodes - of the lungs. We have never met with it except in association with general and, in fact, with very acute medullary cancer.