2. Effusion.—When the bloodvessels are greatly congested and dilated, it usually hap pens that a part of their contents escapes, and the cellular tissue becomes loaded with coagulable lymph, more or less tinged with blood accord ing to the vascularity of the affected part, pro ducing that condition which has been called red induration. This substance, by agglutina ting together the fibres and layers, causes the hardness which is so perceptible on pressing the diseased part. At the same time that this solid deposition takes place in the centre, it is found that the circumference of the inflamed part is soft and cedematous, in consequence of the cells being distended with a fluid which appears to be the serum of the blood. Although the cellular tissue is rendered more firm to the touch by the effusion of lymph, yet, as happens in the other organized structures of the body when attacked by acute inflammation, the co hesion of its fibres is diminished, and it is, con sequently, more easily torn than in its natural state, and its elasticity is also greatly impaired. The preceding changes may be very beautifully observed in the progress of pneumonia, i.vhen the substance of the lungs is passing into that condition which is called red hepatization. I have in my possession a specimen of com mencing bepatization, taken from a lung in another portion of which that change was quite complete. In this preparation a portion of the pulmonary tissue is of' a reddish brown colour, and evidently infiltrated with a solid substance, consisting, it may be presumed, of fibrine mixed with the colouring matter of the blood. The manner in which this deposition took place in the cellular tissue of the organ is distinctly seen, the reddish colour being gradually shaded off till it is lost in the healthy structure.
It sometimes happens that the morbid action now ceases, and that by a process of absorption the interstitial effused matter is removed, so as slowly to restore the part to its proper condition : this is the termination of inflammation to which the term resolution is applied.
3. Suppuration.—It.usually happens in acute inflammation of the cellular tissue, that after the lapse of a certain period, a softening takes place towards the centre of the circumscribed hardness, in consequence of the diminution of cohesion above described gradually increasing, and of the deposition of purulent matter. It is not certain how the pus is formed in the first in stance; several modern pathologists, especially in France, imagine that the lymph and serum which were previously effused experience a change by which they are converted into pus, a theory which is rendered probable by the physical properties of pus so nearly resembling those of the blood : according to other autho rities, pus is a proper secretion derived from the neighbouring arteries. I believe that in the beginning the purulent matter results from changes in the effused matters; but that when suppuration is fully established, the pus is poured out or secreted from the bloodvessels. In the commencement the pus is observed in the cells of the tissue, under the form of whitish spots; subsequently the walls of these inter stices are broken down by the softening alluded to, and the purulent matter is collected together so as to constitute an abscess, which is sur rounded by a rather dense layer of cellular tissue, still retaining the characters of inflam mation. This layer constitutes the sac of the
abscess, and presents at first a rough and reddish surface; but it soon happens that the walls acquire a greater firmness, and that the surface of the sac assumes very much the appearance of a mucous membrane.
4. Ulceration.—When an abscess has thus been formed, the cellular tissue intervening be tween it and the external surface of the body, is removed by the action of the absorbents. This process, which is always preceded by inflam mation, and accompanied by suppuration, is distinguished from various other morbid actions of the absorbents by the term of ulceration. Other instances of ulceration occurring in the cellular tissue might be adduced ; ar. gr. the separation of the slough in carbuncle, after extravasation of urine, &c.
5. Mortification.—If the inflammatory action be sufficiently intense, it causes the destruction of the vitality of the part affected, and pro bably in the manner suggested by Professor Andral. " In the most acute form of hyper oamia,'f' the circulation of the blood is sus pended, and if this stagnation be prolonged so as to become complete, the parts being gorged with blood that is no longer renewed, and which, therefore, soon becomes unfitted to sup port nutrition and life, must necessarily perish, and in this manner gangrene is produced, as in the experiments performed by Dr. Hastings. In these cases the black colour announces the stagnation of the blood, and this stagnation being prolonged, must of necessity lead to gangrene. Such, in my opinion, is the manner in which the species of gangrene usually attri buted to excess of inflammation, is produced." M. Gendrin has ascertained by dissection that some of the vessels are filled with coagulated blood ; whilst others are actually ruptured, and allow their contents to escape. The cessation of the circulation has for a long time been remarked as the most striking character of mor tification ; in fact, that cessation, in whatever manner it may have been induced, whether by inflammation, by continued pressure, by the application of tight bandages to a limb, &c., is in the great majority of instances the imme diate cause of mortification. The consequence of this loss of vital action is, that the natural properties and appearance of the cellular tissue are destroyed ; the affected part becomes dis coloured, usually assuming a black or ash coloured appearance; the proper texture is lost, and the part is infiltrated with a dark sanious fluid, and is subsequently converted into a shapeless mass of pulpy substance, which is cold to the touch, and extremely offensive to the smell, owing to the gases which are generated by putrefaction : in fact, the part is dead, and presents the usual appearances caused by the decomposition of animal matter, con joined with those which result from the pre vious effects produced in the circulation by the inflammatory action, especially the engorge ment of the bloodvessels. These are the changes induced in the cellular substance when it is attacked by humid, or, as it has been called, inflammatory gangrene. In dry gangrene, on the contrary, the black and discoloured part shrivels up, and does not undergo the same changes which are produced by the decompo sition of a texture which is loaded with fluids.