In most instances, the serum having been absorbed, and the walfs of the cavity having been united by coagulable lymph, the latter becotnes slowly organized into a substance which resembles areolar tfssue, but contains comparatively' little of the yellow fibrous ele ment. Cotemporaneously with this change-, vessels are developed in the mass by a series of processes, which, in all probability, closely approximate to those of their formation in the embryo. The resulting structure occu pying what was previously the cavity of the serous membrane, effectually prevents the re petition of such an effusion ; although there is no reason to believe that it confers an ab stract immunity as respects the inflammatory process.
The suppurative inflammation of the serous membranes frequently offers, in its symptoms or causes, few differences from the adhesive variety; but the formation of pus is sometimes discoverable at so early a stage of the dis order, as to render it doubtful how far it may not be considered, not so much a mere form or termination of the disease, but an inflamma tion sui generis. Where pus has been re ceived into the bloodvessels, and circulated with their contents, large collections of this fluid are sometimes seen in these tissues ; these are, however, to be disdnguished front the suppuration which occurs primarily as the result of an inflammatory process. In the latter case, the cavity of the inflamed serous membrane is usually lined by a soft, irregular* and membraniform exsudation, resembling the wall of an abscess, to which the altered tissue may, under these circumstances, be fairly coin, pared. The appearances of the pus present the varieties met with in this fluid generally.
In the most favourable cases, the fluid ra pidly diminishes in quantity ; and the pus-cells, which are incapable of further organization, disappear, the substances which compose them being, in all probability, absorbed subse quently to the breaking up of their structure; while the remaining parts of the exsudation become organized together with the adhering walls of the cavity, and result in the complete obliteration of the serous structure.
In other instances, the suppurative process takes a more unfavourable course ; the pus assumes a sanious appearance and a very of fensive smell ; and, finally, after ulceration or sloughing of the serous membrane is dis charged through the opening into the cavity of the viscus, or into a neighbouring serous membrane, or on the surface of the body.
Sometimes this proces.s appears to be modi fied by the occurrence of a less complete ab sorption. The pus, deprived of certain of its constituents, is slowly transformed into a mortar-like mass, lining the membranous wall by which it appears to be secreted. The sandy or gritty consistence of this substance shows that it contains chiefly the inorganic constituents of the exsudation ; and sometimes the fluid, gradually thickening, passes into a cheesy pultaceous mass, and thence, by long duration, into a cretaceous substance, resem bling that into which tubercle often degene rates.
The so-called chronic inflammation presents no differences which can be called essential ; most of them chiefly referring to the duration and intensity of the process, rather than to any peculiarities in its nature and appearances. For instance, if the general symptoms are less prominent than usual, and the disease pro gresses slowly, with frequent remissions and exacerbations, it is called " chronic." So, also, the same name would be applied to a case which, originally " acute " in the intensity of its symptoms, and the rapidity- of its progress, had overpassed the violence of the first attack ; the effusion remaining with diminished con stitutional disturbance. Or a recurrence of
the inflammation, pouring forth a new eflb sion in and within the already dense and har dened layer of a previous exsudation, is called chronic. In such a rdapse, the unorganized exsudation has been said to be the seat of the secondary inflammation ; but it may be ques tioned how far the inflammatory process can occur in a tissue which is as yet unprovided with vessels : and even were the absence of these as complete as it seems to be, the in flammation of' the lymph would scarcely be a necessary supposition, since it would be dif ficult to deny the possibility of a physical transudation of fluid, derived from the nearest vascular surface, or that of the original mem brane.
Besides these divisions of inflammation ac cording to its duration and results, there are others, in which the process i; compli cated_ by its occurrence in connection with other diseases, or by its dependence upon some specific cause. Amongst these the " hzemor rhagic " effusion, first recognised by Lcerinec, holds a very conspicuous place. In this dis order the inflammatory exsudation is mingled with more, or less blood, which communicates its colour and appearances to the whole mass, in a degree varying with the quantity in which it is present. By longer duration, it separates into two parts: a peripheric layer of whitish or slightly-coloured lymph, which covers the serous surface ; and a fluid which contains the greater part of the blood corpuscles and serum, and is included in the cavity formed by the plastic layer. This liquid portion is only capable of a very slow absorption, and prior to this event it passes through many gradations of colour and appearance. Ge nerally, it slowly loses its red colour ; but in the case of the hmmorrhagic inflammations of the peritoneum, it very frequently becomes darker, and, finally, almost black ; a change which seems due to the action of the intes tinal gases. This conjunction of inflammation and hxnaorrhage occurs in many diseases, but with the greatest frequency in tubercular ca chexia, in fevers, and in other exanthemata. In all these disorders, the mass of the blood is greatly affected, and in many of them suffi ciently so to exhibit marked deviation from the composition and properties of the healthy fluid. And in addition to these, the gene ral conditions of its occurrence, Rokitansky * points out a local circumstance which greatly favours its access ; viz. the previous existence of a plasma, in which organization is com mencing. And he refers this aptitude for hmmorrhage to the probable state of its vas cular apparatus, which, in this early stage of its development, offers simultaneously the greatest delicacy in the texture of its walls, and a deficiency of anastomosis "with the neighbouring vessels ; two conditions which would respectively diminish its capacity of re sistance to any distensive force, and increase the amount and duration of this distension. And in illustration of this his opinion, it may be pointed out, that a granulating surface on the exterior of the body seems closely to imi tate these local conditions; Nvhile the resulting hcemorrhage, often traceable to the congestion mechanically producible by posture, often de pending on exciting causes of a more recon dite nature, affbrds a parallel to some of the effusions noticed above.