Phlegmonous inflammation extends beyond the papillae into the deeper strata of the corium, and sometimes involves not only the entire thickness of that part, but also more or less of the subcutaneous cellular and adipose tissue. It arises very often from the contact of powerful external applications, like burning or cauterizing bodies, with the skin; and sometimes, without manifest external occasion, from an internal cause; sometimes, again, it is produced by the extension of inflammation from subjacent structures, from cellular tissue, muscles, veins, or absorbents.

Just as, under certain circumstances, the phlegmonous arises out of the erythematous inflammation, so also has it several degrees of its own, which pass perceptibly into one another. Its course is in most cases acute, but it is often chronic, and then usually becomes acute from time to time.

The following are the anatomical characters of acute phlegmon of the skin. The redness of the inflamed spot is generally deep (saturated) and dark, it varies in its tint according to the state of the blood, and does not disappear upon pressure; the swelling is moderate, but the firmness of the skin amounts to decided hardness: the tissue of the cutis is found upon section to be red, and to have a homogeneous fleshy appearance; its reticular structure has disappeared; the fat contained in it has lost its characters; and it is also easily torn: the subcutaneous cellular and adipose tissue is minutely injected, and infiltered with a serous fluid. The under surface of the skin presents more or less redness, and a shreddy, granular appearance, and is covered with a viscid exudation, that as it softens becomes purulent.

Chronic phlegmonous inflammation of the skin, such as is developed gradually out of repeated attacks of erythema, and is kept up by various constitutional affections that arise from the suppression of normal or of anomalous excretions, presents very different characters according to the degree of the inflammation, and the circumstances by which it is occasioned and maintained.

The redness is usually dull, and inclines to a bluish, brown, or bronze color.

The tumefaction of the cutis itself is slight: its density is sometimes increased, sometimes decidedly diminished; and it is accordingly firmer than natural, or loosened in texture, and spongy.

The cutis when exposed is sometimes found smooth, uniformly softened and spongy, sometimes it is unevenly granular, and either soft or rather hard. It is covered with a limpid, watery, and colorless, or with a yellowish, yellowish-red, and bloody, or with a thick, viscous, clear or turbid, and yellowish-white, or a yellow purulent, moisture: these products soon change to dirty white, asbestos-like, epidermal scales, and then peel off; or, becoming thickened and dried, form a covering like various kinds of bark.

The subcutaneous cellular tissue is sometimes infiltrated with a viscid serous fluid, and injected; sometimes it is denser than natural, hard and lardaceous, etc.; as the fat disappears, the inflamed spot is depressed beneath the surface of the adjoining healthy skin.

This inflammation terminates in various ways.

Acute phlegmonous inflammation sometimes terminates in resolution, but it leaves the diseased part of a bluish-red color, very susceptible of external influences, and liable to a recurrence of the inflammation for a long time afterwards. It often gives rise to destructive suppuration of the superficial layer, or of the whole thickness, of the corium. That coat is then replaced by a cicatrix, which becomes more or less fixed to, and blended with, the subjacent structures: if inflamed and suppurating surfaces of skin be brought into mutual close contact, they may even unite with one another.

Extensive phlegmonous inflammations and suppurations of the skin, particularly those which are produced by burns and scalds, very often lead to a fatal result, either speedily by exhaustion of the vital powers during the violence of the fever, or more slowly by their drain upon the blood, by congestions, inflammations of internal organs, especially of the lungs (hypostasis), or by exhaustive serous exudations, particularly on the mucous membrane of the intestines. Burns, and especially, as I have observed, burns of the skin of the abdomen, are in a few instances attended by fatal hemorrhage from the bowels, which is most probably introduced by an exudative process.

Now and then, acute phlegmonous inflammation of the skin terminates in mortification: but of this hereafter.

The consequences of chronic cutaneous phlegmon do not cease with the permanent anomalies to which it gives rise in the stratum beneath; these are in themselves of a serious character, but they obtain greater importance from their relation to the integrity of the whole organism. At one time it leaves behind it a condensation and thickening of the skin, in which the subcutaneous cellular tissue also is generally involved, - hypertrophy with induration, and adhesion of the skin to the subjacent structures.

Under certain etiological circumstances, the inflamed spot becomes a vicarious organ of secretion. The exposed skin, having thrown out a few granulations, secretes a thin fluid, which is often very acrid and corrosive, and gradually eats away the substance of the cutis. If at length, the conditions being favorable, the secretion should subside, and the part heal, the cutis is replaced by a dirty brown, vascular, very vulnerable and frail stratum, which, for the most part, produces large scales of epidermis in considerable quantity and is very long in turning pale, and in acquiring the firmness of a sound cicatrix tissue. The whole metamorphoses is a secondary atrophy of the cutis occasioned by the inflammation.

Chronic inflammation of the skin frequently ends in ulceration, and especially is this the case when, from some internal or external cause, the chronic is rapidly exaggerated to a more intense degree of inflammation, or when inflammation returns at a part where the change into cicatrix tissue is going on. Suppurative and sanious destruction, in various forms and to different extents, that is to say, ulcers, then ensue with more or less rapidity.

It may happen that several of these terminations of inflammation exist near together, or are associated with a continuance of the inflammation.