The anatomical characters of this form of inflammation are, -

(1.) A dark, dull redness inclining to brown, injection, and a varicose state of the vessels.

(2.) Increase of bulk; the mucous membrane becomes thick and tumid; the swelling of the papillae and follicles renders its surface uneven, especially if the process have been of long duration and the glands be abundant; its tissue, becoming denser and more compact than natural, is hence also -

(3.) Tough and resisting, and is with difficulty torn: it is more firmly connected, too, with the subjacent tissues, and they become swollen, dense, and tough (hypertrophied).

(4.) The secretion is a grayish or yellowish-gray, opaque, viscid mucus.

Chronic inflammation usually leaves behind it a permanent tumefaction, or hypertrophy of the mucous membrane, and a continual excessive secretion of a grayish-white and milky, or of a glassy transparent pasty mucus, - a blennorrhoea, which may or may not be attended with an exuberant formation of epithelium, and in which, accordingly, the epithelium is either rapidly thrown off from an almost bare, and, as it seems, excoriated mucous membrane, or accumulates over the whole, or over parts of the surface, and thus forms a complete laminated covering for it, or patches of various thickness here and there upon it.

The hypertrophied membrane itself is pale, or more commonly of a rusty brown, or slate-gray, and after a time, of a dark-blue color; it is thick, compact, and firm: when it is uniform in thickness its surface is smooth; sometimes, from the great increase in the size of its papillae and follicles, it is warty and rugged; and lastly, even various duplica-tures and prolongations may be formed upon it.

The two last-mentioned inequalities of the membrane are permanent, immovable folds of the membrane: they constitute what is called the mucous or cellular polypus, or the vesicular polypus.

These polypi are processes of the mucous membrane, of various thickness and length. In shape they are spheroidal or elongated, or like ninepins or cylinders; and their free extremity is thick and blunted. The mucous membrane and the tissue beneath it becoming hypertrophied at particular round circumscribed spots, form a somewhat flattened convex tumor, and progressively change into a honeycombed cellular tissue. Little by little the tumor drops into the cavity of the organ, dragging with it the surrounding mucous membrane, by which, as by a comparatively thin, and more or less elongated pedicle, it remains attached. The polypus then consists of a cylindrical prolongation of mucous membrane, which contains a cord of submucous tissue, and of a truncated extremity or knob, at which the tissue proceeds to form itself into a honeycombed cluster of vesicles and follicles, and becomes lobulated like a cauliflower; it presents a system of dilated capillary vessels; now and then it becomes turgid; it secretes a jelly-like mucus in its interstices, and when that is discharged, it shrinks.

Polypi do not occur with equal frequency on all mucous membranes. They are especially frequent upon those membranes, and parts of membranes, that are bulky and thick, and have abundance of follicles, and that are frequently attacked with catarrh. Such are the Schneiderian membrane, the mucous coat of the stomach, especially its pyloric half; that of the large intestine, particularly of the rectum; and the mucous membrane of the uterus, more especially about its cervix. The cellular polypus occurs, but less frequently, in the pharynx, the larynx, and oesophagus, in the small intestines, the urinary bladder and urethra, - though it is somewhat frequent in the female urethra; it is extremely rare, and indeed almost never occurs, in the trachea and bronchi, in the Fallopian tubes, and in ducts generally.

The catarrhal origin explains why they occur in such great numbers, whether separately or, as they mostly exist, in clusters, upon one mucous membrane.

In their thrusting the mucous membrane before them as they enlarge, and in their even protruding into a cavity, and hanging in it by a pedicle of mucous membrane, the form of the polypus is often imitated by various new growths in the submucous structures, especially by lipoma, fibroid tumors, and even by cancer. Several of these new growths have been distinguished from the mucous polypus by the names of fibrous and fleshy polypi.

A point of some importance is the condition of the submucous tissues during catarrhal inflammation and blennorrhoea. The increased sensibility of the mucous membrane gives rise to very frequent reflex movements in those which are irritable, and when the course of the process is chronic, they become hypertrophied, as well from the permanent increase in the quantity of fluids arriving in them, as from the process itself. At length, if there be much hypertrophy, the irritable and contractile submucous tissues gradually become paralyzed, and their respective cavities and canals are permanently dilated.

Moreover, chronic catarrhal inflammation sometimes terminates in suppuration and ulcer, - an event which more frequently occurs, and with more rapidity, when an acute inflammation supervenes. In that case the redness becomes more vivid, and seems as if it were identified with the mucous membrane, while the membrane itself is changed into a friable tissue, is swollen with blood, and resembles a sponge, or a spongy gland. Matter appears, either extended, as a more or less smooth coating, over the surface of the membrane, or collected in small quantities in its substance; and in this manner the tissue gradually disappears, - the whole process constituting the catarrhal (simple) suppuration, or catarrhal phthisis of mucous membrane. It leaves behind it an ulcerated breach of substance, corresponding in size to the extent of the inflammatory process, - a catarrhal ulcer, which may be limited by, or may extend deeply into, the adjoining submucous tissue. If, in the former case, the ulcer be small, it heals readily, its base becoming a dense cellular tissue, and the surrounding mucous membrane being drawn in, and at length becoming adherent, over it. An ulcer of larger extent acquires a fibro-callous base, but does not cicatrize; it remains bare, and sometimes obtains a smooth covering like serous membrane: in canals with soft walls its tendency to shrink occasions strictures; and it often, from the application of various powerful agents, becomes the seat of chronic inflammation or of gangrene, sloughs away, ulcerates anew, etc. The character of the catarrhal ulcer probably varies according to the nature of the catarrh.

Both acute and chronic catarrhal inflammations, and the various processes in which they terminate, may affect the follicles of a mucous membrane principally or alone. The walls of the follicle then redden, and the parts adjoining, as well as the follicle itself, become injected, tumid, and enlarged: its secretion diminishes in quantity or is suppressed; but sometimes it is more abundant than natural, and either pours freely forth, or being retained in the cavity of the follicle, becomes inspissated, and undergoes various other secondary changes. The result of this process sometimes is a permanent enlargement (hypertrophy) of the follicle, a dilatation of its cavity, or an habitual profuse secretion of a tenacious glassy mucus - -follicular blennorrhoea. Sometimes the process terminates in suppuration of the follicle, and follicular ulcer. It becomes converted into an abscess, which usually bursts through, and discharges itself upon the internal free surface of the mucous membrane: a small, round, crater-like ulcer is then found situated at the top of a rounded conical tumor, and having a hard base: as the suppuration of the follicle proceeds, the ulcer becomes larger and shallower, and when the follicle is quite destroyed, is encircled by a border of loose mucous membrane; it then extends superficially, or which is rarer, deeply amongst the submucous tissues.

This process is mostly seen on membranes which have follicles in abundance, and are disposed to catarrh; on that of the air-passages, for instance, particularly in the larynx; or in the intestinal canal, especially in the large intestines, where it produces very extensive devastations.