Section Vii. the Pleura.

Like other serous membranes, the pleura is liable to inflammation, both acute and chronic, with their results—plastic, serous, or purulent effusions, adhesions, etc.

=Inflammation.= The first change which is observed in inflammation of the pleura (pleurisy) is a loss of the shining, transparent appearance of that membrane, it becoming dull and opaque. Red injected vessels, in minute ramifications, sometimes radiating from single points, in others more uniformly diffused, will be noticed. Often the surface will present a red mottled appearance, with here and there small points of extravasation. This condition having existed for from six to twenty-four hours, certain results follow—at least in the acute form—which give rise to what is known as

=Plastic Effusion.= Soon after the inflammatory process is fully established, there will appear upon the surface a small quantity of clear fluid, which, as it increases in quantity, undergoes coagulation, and thus gradually covers the surface with a jelly-like layer of variable thickness and honey-comb surface. A thin fluid of a straw color, will be found oozing from the surface, which is increased as the coagulated membrane is cut or torn. This condition may be extended over the whole surface of both the costal and pulmonary pleura, or may be confined to a limited portion.

=Adhesions.= The two layers of the pleura being in immediate contact, the consequence of this effusion of coagulated lymph will be an early adhesion of the applied surfaces. This is accomplished by a blending of the layers of coagulated matter in contact, and a gradual organization of the same by an extension of blood-vessels from the pleura into the new formation. At the same time that these changes are progressing, the watery part of the exudation trickles down to the most dependent portion of the cavity, and there forms a serous or sero-purulent accumulation. Adhesions are more frequent at the upper portion of the lungs, but may be found at any point, as between the inner surface and the mediastinum, or the lower surface and diaphragm; or, from repeated attacks of pleuritis, involving different portions of the serous membrane, the whole of the exterior of the lung may become united to the adjoining surfaces.

The strength of the adhesions will be somewhat in proportion to their age, those of long standing requiring considerable force to break them up, and in many instances the lung tissues becoming lacerated before the attachments can be torn away.

Unusual thickness of the pleura is often found at points where no adhesions exist, this being unquestionably the result of the effusion of plastic matter into the subserous tissue during an attack of inflammation.

=Serous Effusion.= While in the majority of cases of pleuritic inflammation, we shall find plastic effusions followed by adhesions of the inflamed with the adjoining surface, in some instances a serous or watery fluid is rapidly poured out, and, accumulating in the pleural sac, constitutes hydrothorax or dropsy of the chest. The fluid in these cases may present a variety of shades of color, from a pinkish or light straw color, to a dark brownish shade. It may be transparent or opaque, and generally will be more or less albuminous. The quantity may vary from a few ounces to three, four, or five pints, or more. When in large quantity, the lung will be found more or less collapsed, shrunken, and pressed against the posterior walls of the chest and spinal column.

In the general dropsy attending diseases of the heart, kidneys or liver, effusions may take place into the pleural cavities, to such an extent as to give rise to great dyspnœa from compression of the lungs.

=Sero-Purulent or Puriform Effusions=, consist in the presence of a quantity of granular particles with albuminous matter, which subside to the bottom of the vessel when drawn off, and always contains floating flakes of lymph. It may be found in cases of both acute and chronic pleurisy, and, like serous effusions, may be found in large quantity.

=Purulent Fluid=, as found in the cavity of the chest, consists of a white or cream-colored, opaque, and homogeneous fluid, combined with more or less albuminous matter, in the form of shreds and flakes, yet destitute of the granular matter of the sero-purulent fluids, and not separating into a fluid and solid portion when at rest, as is the case with the latter.

It is a fact well established, that genuine purulent matter may be formed in the pleural cavity, as well as in other serous cavities, without ulceration of any portion of the surface, or discharge of an abscess into the same, it being the result of a more advanced stage of the process which gives rise to the serous or plastic effusions. It may be secreted directly from the capillaries of the inflamed surface, or, in some instances, it would appear to be derived from the organized false membranes, which have taken on a suppurative action.

=Pneumothorax.= Air may enter the pleural cavity, by perforation of the walls of the chest from external injury, or, as is more common, by the destruction of the pulmonary portion of the membrane, from the bursting of a distended air-cell, or from softening of tubercular deposits, or bursting of an abscess. If there are but few or no adhesions, the accumulation of air in the cavity may be accompanied by a more or less complete collapse of the lung, as in hydrothorax. This condition, during life, is not readily distinguished from emphysema, both being accompanied with similar oppression in breathing, distension of the chest, and displacements of the heart, and with increased clearness on percussion. Serous or sero-purulent effusions will frequently accompany the presence of air in the cavity, and thus give rise to many of the peculiar physical signs which may have been noticed during life, as metallic tinkling, a splashing sound on shaking the chest, etc.