The events of inflammation are mainly in cluded in the preceding sketch of the effusion which constitutes its most important feature : in this manner adhesion, suppuration, ulcera tion, and more rarely' sloughing, occur. But they also happen, though with less frequency', as secondary affections of the serous mem branes, in connection with diseases of the viscera or cavities which they cover. Thus, a morbid process in the immediate neighbour hood of a serous membrane frequently causes a slight enctsion, which is followed by an ad hesion of its visceral and parietal layers ; an effect which is usually attributed to an " irri tation " of the part by the disease. And as this process generally- precedes any similar extension of ulceration to these membranes, it has the salutary result of sealing up their in terior, and thus of preventing what would otherwise be a serious or even fatal effusion into their cavity. Their destruction by the communication of an ulcerative process in their immediate proximity may be called by the same name ; but it often more resembles sloughing in the rapidity of its course, and in the imperfect absorption of the broken down textures. So also where softening of these tissues happens, it almost invariably depends upon an action which primarily affects the subjacent viscera, and gradually implicates their serous covering.
Tubercle. — The deposit of this morbid product in the cavity of a serous membrane constitutes but a part of the general tuber cular cachexia; and in the majority of in stances, it only occurs after the disease has been localised in some other organ ; often, indeed, after it has already implicated the respiratory apparatus. And even in tbose cases in which its symptoms precede other manifestations of the disease, it appears ex tremely probable that the lymphatic glands of the immediate neighbourhood have been the original seat of the deposit, and that from thence it has, as it were, extended to the par ticular serous membrane.
Occasionally, the tubercular matter is de posited in and amongst the effused products of inflammation, so that the two processes appear to tnerge into each other, with a similar mingling of their products. This occurrence of tubercle in connection with inflammatory exsudation has been minutely described by Rokitansky, who considers that a complete metamorphosis of the latter substance into the former does, in some instances, obtain. But from the difficulty of procuring direct evidence upon this point, e. of examining different portions of the same effusion at different periods of its dura tion, one may be allowed to doubt whether such a transmutation, or even a substitution, is really effected.
Generally speaking, the coexisting inflam mation plays a more subordinate part.
Where the tubercular matter is thus compa ratively uncomplicated, it occurs in the form of greyish semi-transparent granulations, of about the size of a millet-seed, or rather larger. The situation of these is usually on the inner surface of the membrane, which they render irregular by their presence, so that on removing a tubercle (which is easily peeled off' from the subjacent texture), a depression of a size which corresponds to it is exposed, in which the serous membrane has lost its smooth and shining character, and has become dull and somewhat opaque. Besides this, which is the ordinary form of tubercle in these textures, other and smaller varieties often occur : and where a large quantity of the deposit is present, more or less exsudation unites the whole into a layer ; in which, however, the granularity of their developement can still be discerned. Usually, a certain amount of serous fluid is also present, the quantity of which has some relation to the extent of the disease. In the peritoneum, however, its quantity is for the most part insignificant ; and the cavity of the serous membrane is completely filled by a thick and solid, yet granular mass of tuber cle, by which the viscera and abdominal parieties are completely matted together. Sometimes, but rarely, the texture of the serous membrane itself, or the subserous areolar tissue, becomes the seat of the de posit ; in these cases its quantity is small. The after-changes of tubercle in these tissues may lead to suppuration and ulceration, or to a slow absorption of the organic constitu ents of the mass, and a cretification of the remainder ; but in the greater number of cases, the patient dies of the general disease without either of these events having hap pened.
Cancer of these tissues is comparatively rare : and of those instances which do occur, many are scarcely affections of the serous membranes themselves, but ought rather to be considered as secondary, and dependent on a mere local proximity. Thus, a neigh bouring cancerous tumour, by the progress of its growth, conies into contact with a serous ntembrane, and, as its size increases, gradually implicates this structure in its own diseased mass. Sometimes they are primarily at tacked ; yet even here, other organs gene rally suffer at the same time, and either com plicate or mask the local disease.
The carcinomatous deposits themselves offer few special peculiarities of appearance. The harder or scirrhous forms are seldom seen ; the softer varieties, viz. the gelatini form or areolar, the medullary, and the me lanotic, being those to which they are most liable. For a description of these the reader is referred to the article ADVENTITIOUS PRODUCTS.