B. Chronic Inflammation

Chronic inflammation presents itself in three different forms or kinds: a. It commences as a latent, and continues as a lingering inflammation: though ordinarily moderate in its degree, from time to time it becomes more severe. It furnishes an exudation that is continually augmenting in quantity by gradual accumulation, and occasionally also by a more sudden increase. It sometimes affects several serous membranes at once; but sometimes, especially if they should be near together, it attacks them one after another.

The redness of serous membranes, which inflame in this manner, is dull, and inclines to brown; the injection is coarse, and the membrane is extremely dull and perfectly opaque: its surface is quite lustreless, rough, and, as it were, rugous. It is much thickened too, for not only are the membrane itself and the subserous cellular tissue infiltered, but also other adjoining structures, especially fibrous structures, which are closely connected with the diseased membrane; and the infiltrated matter gradually solidifies in them all. Hence the serous membrane is increased in density and compactness, and cannot be so readily torn as in its natural state, but it may with ease be stripped off the subjacent tissue.

The persistency and occasional exaggeration of the process render the exudation always an abundant one; for the inflammation is on the one hand continually adding to its amount, and on the other preventing its absorption. The exudation is always characterized by the small quantity of its plastic portion, and the excess of that which is not coagulable. The former portion consists of a plastic layer upon the inner surface of the membrane, of a pale reddish, or grayish, color, and of slight thickness; the latter is a perfectly clear, a pale yellowish, or a greenish, serous fluid: sometimes it contains a certain quantity of coagulable matters of little plastic power, which swim about as soft albuminous flakes, or form a shaggy precipitate on the inner surface of the original deposit, or lastly coagulate in large lardaceous masses, which usually occupy the deepest space in the serous cavity.

When the inflammatory process subsides, the serous effusion is gradually absorbed: if any of it remain and prevent mutual contact of the walls and duplicatures of the serous membrane, the plastic exudation increases in density, yields up the moisture (water of crystallization) contained in it, and changes into a firm cellular, or rather into a fibro-serous plate: but if the serous fluid be entirely absorbed before the organization of the plastic part is completed, the latter forms a dense fibro-cellular bond of adhesion, with which the serous membrane intimately unites, and seems identified.

ft. An inflammation originally acute may, after having deposited its exudation, become chronic. Such a termination of an acute inflammation occurs chiefly when its exudation is one which degenerates into pus or is actually purulent: and there is no question, that the state of chronic inflammation is kept up by the contact of the membrane with the exudation.

The serous membrane seems changed into a spongy, granulating layer which is colored with various shades of red; it secretes a purulent exudation, or one that degenerates into puriform matter; and a yellow soft villous coating, which is in process of solution, or a somewhat thick pus adheres to the interior: - the serous sac is converted into a closed or encysted abscess.

In the most favorable case, such an effusion is entirely absorbed after the subsidence of the inflammation; the serous membrane and the or-ganizable substance which clings to and invests it gradually change into a dense fibro-cellular tissue, and the opposite laminae of it unite in one tough adhesion. During this process, the serous membrane, as such, is, in fact, destroyed.

In other cases, the exudation, after having lost some of its constituent parts by absorption, and undergone a change in its ingredients and elementary composition, is subjected to various metamorphoses; while the serous membrane, and the layer investing it, become converted into a dense fibroid plate. The exudation is gradually inspissated, forms a cream-like, and afterwards a cheesy, whitish-yellow, pulp, and in the end becomes chalky: or else there remains behind, within the false membrane, - probably as a consequence of the exudation containing an abundance of animal lime, - a whitish fluid like lime-water, which incrusts upon the inner surface of the membrane, and renders it smooth and polished like gypsum, or rough and sandy, like mortar. Or lastly, the pseudo-membranous sac contains a fatty glutinous fluid, which is, for the most part, of a brownish-yellow color, and is mixed with numerous minute glittering scales (fat-crystals), which cling in thick clusters to its inner surface.

In the most unfavorable case, the purulent exudation becomes sanious, and for the most part, of a greenish color; at the same time, in some instances, gas is evolved, and the exudation assumes a most offensive pungent odor, like that of garlic, phosphate of ammonia, or sulphuretted hydrogen. Under these circumstances, the serous membrane not unfrequently ulcerates, or sloughs at some small and circumscribed, or at larger spots; sometimes the ulceration extends into the subserous structure, and opening of the serous sac takes place, and its contents are spontaneously discharged, either externally or into another cavity. - (Phthisis meinbranae serosae ulcerosa).