Inflammation of cellular tissue (inflammatio teloe cellulosse) is a disease of much importance, not only on account of the circumstances attending its occurrence in that tissue itself, but also because, as a consecutive and as an allied affection, it accompanies the inflammation of all structures which are imbedded in it. Thus inflammation of serous and fibrous membranes, of muscles, lymphatic glands, vessels, nerves, etc, is attended by inflammation of the cellular tissue that surrounds them. Its course is sometimes acute, sometimes chronic. Acute inflammation affects principally large tracts of cellular tissue, such as that beneath the integuments of the trunk and limbs, the cellular tissue accumulated in the neighborhood of the caecum and rectum, the deeper layers of the same structure in the neck, and that in the me-diastina: and it is very often remarkable for its great extent, and for the devastations which it causes. Its anatomical characters are as follow:

The appearance of the cellular tissue varies according to the degree and the character of the inflammation and the condition of the blood. It is swollen, injected, and of a bright or a deep red color; it has in every case lost its extensile and elastic properties, and may be easily torn; among its fibres, and between its laminae, inflammatory products are effused, which differ in having more or less plastic qualities; and are, accordingly, either a viscid, and turbid or flocculent, serous fluid of a pale-red, or yellow, or grayish color; a yellowish-red, gelatinous, and more consistent exudation; a brownish-red, fibrinous product, which fuses with the tissue into a hard, but yet fragile mass: or a dark-red (hemorrhagic), discolored effusion. The inflammation always involves, the adjoining organs, more especially membranous expansions, serous and fibrous membranes, and the integuments. The disease in this last instance is that known by the name of Pseudo-erysipelas.

The adipose tissue presents a similar kind of injection and reddening; when the inflammation is slight, it is percolated by a viscous, turbid, oleo-serous fluid, which gives the fat vesicles a pale, yellowish-red, translucid, jelly-like aspect. In inflammations of a severer character, the adipose tissue becomes brownish-red; the contents of the fat vesicles liquefy and escape through their walls, and a plastic exudation takes their place, and gives to the whole tissue a uniform granular appearance, and a certain degree of firmness.

Acute inflammation of cellular tissue, when moderate in degree, usually terminates in resolution, that is to say, by the complete reabsorption of the inflammatory products; merely some cedematous swelling, or a tendency to oedema remaining in the part which has been inflamed.

In other cases the inflammation leads to induration and hypertrophy of the tissue. The inflammatory product becomes organized, and the mass of the cellular tissue hypertrophied; and hence, as well as from the unnatural adhesion the new substance produces between the old strata of the tissue, the entire structure becomes denser, more compact than natural, or as it is called fibro-cellular.

Inflammation, when it reaches a high degree, very often proceeds to suppuration. As the firmness of the inflammatory swelling subsides, a serous exhalation reappears in the tissue, the product of the inflammation becomes resolved into pus, and thus the cellular tissue in the centre of the inflamed spot, and afterwards throughout it, is found infiltered with a sero-purulent, and at length with a purulent, fluid. Yellowish or yellowish-red bodies which, though shreddy, are still somewhat compact and tough, are often found mixed with the matter: they are not sloughy cellular tissue, but the residue of the inflammatory product, and are therefore named eiterpfropfe - plugs of purulent matter - though, indeed, fibres of the cellular tissue are certainly interwoven amongst them, or even larger shreddy portions of it may adhere to them.

The points of matter, coalescing as the tissue is destroyed, unite into larger collections; and these extend further, either by forming sinuous canals, or by enlarging equally in all directions. If in the latter case, the matter be situated in the subcutaneous cellular tissue, it will separate the integuments to a great extent from the deeper structures, and will perforate muscles and aponeuroses, or open into serous cavities, into the intestines, etc.

Matter may also collect in cellular tissue from mere gravitation; for abscesses are met with, none of the contents of which, or at least but a part, have been produced by inflammation in the spot where they are found: the matter has gravitated thither from some part more or less remote.

In whichever way the abscess may have originated, it not unfrequently becomes encysted, that is to say, circumscribed by a cellulo-vascular granulating membrane. This membrane is the product of a secondary inflammatory process at the confines of the suppurating part, and itself secretes pus. It often remains for a long time in this state, and at length usually produces exhaustion by the continued secretion of matter from its walls. Occasionally, however, the formation of matter ceases, the walls become converted into a dense cellulo-fibrous tissue, and the matter is entirely reabsorbed, or part of it is absorbed and the rest inspissated. As these changes take place, the sac gradually diminishes, until at length either its walls unite, or it is reduced to a cyst of trifling size, compared with its previous dimensions; the walls of such a cyst are thick, composed of obsolete callus, and incrusted on their interio; and its cavity is filled with a calcareous pulp or concretion.

Lastly, the product of the inflammation is sometimes of a peculiar nature, and leads to destruction and sloughing of the cellular-tissue (to actual necrosis textus cellulosi). The tissue then breaks down, as it were, into a crumbling, or a shreddy, friable mass, and becomes infiltrated with a dirty brown or greenish sanies. Not unfrequently under these circumstances, a quantity of gas is formed, which distends the whole of the diseased part.

Inflammation of cellular tissue may be a primary affection, or, as is very frequently the case, it may be secondary. Each form assumes a serious character in particular localities; as when it attacks the cellular tissue of the trunk or limbs; or that between the pericranium and the galea aponeurotica of the head; that near the submaxillary (Ludwig), or the thyroid glands; or that which accompanies the trachea, pharynx, and oesophagus down to the mediastinum; or the tissue upon the lumbar vertebrae, or on the iliacus muscle; or that in the neighborhood of the caecum (perityphlitis), or of the rectum (periproctitis), or bladder (pericystitis); as well as interstitial cellular strata, especially the submucous tissue of the stomach, intestinal canal, etc.

The inflammation, whether primary or secondary, may have a more or less distinctly marked exudative character; as is illustrated by phlegmatia alba, as it is called, amongst the primary inflammations, and by the numerous instances of inflammation which occur in cellular tissue by metastasis, after acute exanthemata, typhus, etc, amongst the secondary. They are often associated with exudative processes on membranous expansions, especially such as adjoin mucous and serous membranes.

Moreover inflammation of cellular tissue is frequently derived from that of other parts. It uniformly accompanies the inflammation of structures which are imbedded in it; especially inflammation of veins, and lymphatic vessels, lymphatic glands, nerves, muscles, serous and fibrous membranes, etc. It is generally subordinate in degree to that which prevails in the actual seat of disease; though there are occasional exceptions to this rule, the inflammation in the neighborhood of the actual seat of disease sometimes going on at isolated points to the more advanced degree, particularly to suppuration. Such is the case, for instance, in inflammation of veins.

Inflammation of the adipose tissue may subside, occasioning merely some loss of the fat?: in process of time, however, the loss is supplied again.

But in other cases, severe inflammation is followed by coalescence and obliteration of the fat vesicles, and consequently by a marked shrinking of the part which has been inflamed.

Inflammation of this kind often terminates in suppuration; and the adipose tissue becomes converted into a yellowish-red pulpy mass, which is infiltered with a fatty purulent fluid.

Lastly, a fibrinous inflammatory product is sometimes seen in the fat vesicles; it solidifies in them, changes into a cheesy mass, and in the end even becomes cretaceous. The wall of the vesicle is then found thickened, it contracts upon its contents, and bears traces of its previous congestion in the slate-gray or blackish-blue color with which it is tinged. This change is principally observed on the fatty tissue of the omenta, and appendices of epiploacae; especially in tubercular subjects, in whom peritoneal inflammations have occurred and have been attended with tubercular exudation.

Chronic inflammation of cellular tissue is distinguished by the following characters: the tissue is but slightly injected and reddened; though where it is exposed, as it is at the base of the ulcers, its color is a deep red, tinged with various shades of brown, coppery, rusty yellow, violet, etc.: it is also denser than natural, and contains a viscid serous fluid, which when ulcers exist, filters through to their surface.

Inflammation of this kind does not proceed to suppuration, except perhaps at a few small isolated spots: it tends rather to induration and that at an early period. The tissue is then very compact, and so tough that it makes a creaking noise when it is cut: it is also pervaded, and as it were identified, with a gelatinous matter, or an albuminous substance resembling lard. The tissue is found in these various conditions beneath and around chronic ulcers, in the neighborhood of fistulse, after repeated and habitual, or mismanaged attacks of erysipelas, or as a consequence of mechanical hypersemia, or congestions arising from varicose veins in the lower limbs, in cases of elephantiasis, etc.

An inflammatory process of a peculiar kind occurs in new-born children, and is known by the name of induration of the cellular tissue (sclerosis tehae cellulosae). It occurs on the trunk, especially on the whole of the lower part of the abdomen, as well as on the thighs, and the cheeks. The subcutaneous fatty and cellular structures are moistened by a yellowish viscid serum, the fat is condensed and forms a yellowish or brownish-red hard granular mass, and the skin covering it is tense, as firm and resisting as a board, glistening and pale or of a yellowish-red color. The numerous theories which have been broached as to the nature of this induration of cellular tissue and its etiological relation with disorders of internal organs are daily proved to be unsound. Thus it has been traced to diseases of the liver or lungs, to permanent patency of the foetal canals and cyanosis, and to irritation of the stomach and intestinal canal. But these conditions, and even the icterus, which is its most frequent associate, are all accidental complications. The induration is unquestionably an independent disease (occasioned by disorder of the functions of the skin of the new-born child), and, just as in burns of the integuments, its seriousness and danger are directly proportioned to its extent.