3. Softening Of Serous Membranes

There is no such disease as primary softening of these membranes: when it does occur, it is consecutive, and in the peritoneum and pleurae, ensues upon prior softening of the stomach, intestine, oesophagus, and lungs. The mode in which the serous membrane suffers is the same as has been described in the account of those diseases.

4. Adventitious Growths

Some of these have been mentioned as products of inflammation. There remain to be noticed:

A. Lipoma

This occurs in subserous cellular tissue, but is an unusual disease; it consists generally of a small and lobulated mass of fat. which projects into the cavity of the serous membrane. A somewhat remarkable form is that described by J. Müller under the name of lipoma arborescens; it occurs on synovial membranes, especially in the knee joint.

B. Cysts

These, on the whole, are rare growths on serous membranes; though there are exceptions to such a rule in the instance of some serous membranes, and even of particular regions and particular prolongations and duplicatures of them. Thus in the peritoneun, for instance, cysts are frequently found on that part which invests the sexual organs of the female, especially on the broad ligaments and peritoneal coverings of the ovaries and Fallopian tubes; on the great omentum the same is the case, and on the tunica vaginalis of the testicle, which in this respect bears a remarkable analogy to the sexual portion of the peritoneum in the female. Equally remarkable is the fact, that when cysts are formed on serous membranes, it is chiefly on portions connected with organs in which cancer is of frequent occurrence.

There are two different ways in which cysts are developed; and in this respect their development is analogous to that of secondary cysts upon and within anomalous serous and fibro-serous membranes. In one case, the cyst is formed upon the inner free surface of the serous membrane, and for the most part is a vesicle with very delicate walls: such cysts are sometimes very numerous; they are usually of small size, and have broad bases, rarely being attached by a pedicle. In the other case it is formed deeper in the parenchyma of the membrane or in the subserous cellular tissue - in the wall of the serous sac, and is often situated as in the broad ligaments, between two serous layers; it thrusts the membrane before it, and at length falling into the cavity, remains suspended only by a serous cord or pedicle, which is sometimes several inches long. Cysts of this kind very often have thick walls, and frequently attain a considerable size: they occur singly or in small numbers, and almost only in the neighborhood of the internal sexual organs of the female; those which have long pedicles are often observed at the fimbriated extremity of the Fallopian tubes.

The contents of the cysts are most frequently serous; sometimes they are thin and watery, sometimes thicker and mixed with albumen or with a fluid like synovia; occasionally other substances are found in them, which may be colorless or colored, gelatinous, like gum or glue (colloid), or fatty. Cysts with contents of the last-mentioned kind are often found in the omentum, and sometimes, besides the fat, they contain also hair, bones, and teeth.

C. Fibroid Tissue

One form in which this tissue presents itself, is that of condensation of the serous membrane, and of the cellular layer beneath it: it assumes the appearance either of milk-white, more or less circumscribed stains, which, after a time, become smooth or uneven plates of various thickness; or of bluish-white, tough, separate granulations (so called cartilaginifieation of serous membrane). Another form is that of fibroid exudation upon the inner surface of the membrane. The present head might include also the concretions which are found free in serous and synovial membranes, but they will be treated of in a subsequent part of the work. Moreover various fibroid growths found in the synovial membranes of joints, are formed from exudation accumulated in particular spots; they are villous and laminated, or they form clusters of small subovate bodies that resemble melon-seeds (Mayo). Bursae are sometimes filled with balls of exudation which are undergoing a change into fibroid tissue.