On either side of this principal fold the lateral pliese arrange themselves, inclining more outwardly in proportion as they occupy a still lower place in the cervix. But in these cases the curves of the lateral plicw are often very abrupt — the laminx rising obliquely up wards, and then making a sudden downward bend like the ends of the leaves of a lily. This arrangement of the plicm I think I have more often observed upon the posterior wall of the cervix, where the laminw are usually' thicker and bolder than upon the anterior wall, upon which the arrangement first de scribed appears more comnionly to prevail. But so various are the forms which the prin cipal folds of the mucous lining of the cervix assume, that it is not possible to fix upon any one instance whose description, however mi nute and accurate, will serve as a strict ex ample of the rest.
The more perpendicular the arrangement of the Om, the nearer is the approach to that form which is most conimonly found in the terminal part, or neck of the uterus, in the mammalia generally, where the folds al most invariably take the direction of the long axis of' the canal, reminding us of the ar rangement of the plicx in the Fallopian tube already described.
After repeated pregnancies these plicze become much thickened and the folds more prominent, while their extremities exhibit a swollen and bulbous appearance resembling leaflets attached to the branch of a tree. Hence, apparently, the origin of the old term arbor vitw, by which this structure was com monly designated; while to the more closely arranged plicm, springing from a central shaft or raphe, the term penniform raga' is more strictly applicable ; and to those cases in which several parallel folds, after ascending ob liquely, form a series of lateral arches, or suddenly bend over and then downwards, the title of plica palmatrE, or as some employ it, palma plicaks, seems more appropriate.
Thus upon both walls of the uterine cervix the mucous membrane, being of greater extent than the surfaces which it lines, is gathered into folds whose offices will be presently more specially considered. At ,the lateral lines of junction of the two cervical walls, where a crease or furrow is formed by the sudden bending of the parietes, an imperfect raphe is sometimes found, uniting a portion of the plicte ; but more commonly the laminm of one surface either pass over and become united at their extremities with those of the oppo site side, or else upon reaching the lateral angles they split up into smaller divisions, which are again gathered into the single folds upon the opposite side, their junction being then effected by the interposition of a cribri form surface.
The central raphe and lateral plicm pro ceeding from it, under whatever form they may appear, constitute together a series of primary folds, from which others of a secon dary order are produced. These emerge from either side of the lateral phew, and, crossing the ftirrows between them, subdivide again and again until the whole surface presents that cribriform aspect which can be just dis cerned by the naked eye, but cannot be accu rately examined without the aid of the mi croscope. Here also are found in countless
numbers these mucous crypts, which appa rently furnish the peculiar secretions of this portion of the uterus (fig. 432.).
Structure and arrangement of the tissues composing the uterus.— The uterus is usually described as consisting of three coats, viz., an outer or serous, a middle or muscular, and an inner or lining membrane, commonly termed the mucous coat. But these coats cannot, like the three coats of an intestine, for example, be separately displayed, because each passes so imperceptibly into the others, that although to the naked eye an apparent distinction may be observed, this distinction in a great mea sure vanishes under the application of the microscope.
Peritoneal coat. — The outer serous coat, which constitutes the thinnest of the three component tissues of the uterus, is formed of the centre of the principal fold of the broad ligament, which is closely applied to the uterine body and fundus, and to a portion of its neck.
It is of great importance to the com prehension of certain points in the pathology of the uterus, to be hereafter considered, that the relations of this peritoneal covering to the proper structures of the organ, a.s well as to adjacent parts, should be accurately deter mined. The most important of these rela tions are shown in .fi'g. 433., representing a vertical section of the pelvis and its con tents. In this view the reflexions of peri toneum over the centre of the uterus are shown. The membrane, after lining the abdominal walls, and covering the fundus, and a portion of the posterior surface of the bladder, is suddenly arrested in its descent at a point very nearly opposite to, but some times a little below the internal os uteri, and therefore about the seat of junction of the body with the neck of the uterus. Here the membrane forms a sharp fold or angle, and becomes immediately applied to the anterior face of the uterine body, while the cervix, which lies in great part, if not entirely, below this level is left uninvested. The peritoneum, then, after ascending over the anterior uterine wall, covers the fundus and sides of the organ, and descending upon the posterior surface, it remains closely adherent to the tissues be neath, until it reaches the level of the anterior point or reflexion. At this point the perito neum becomes much more loosely connected with the uterus by the interposition of a quantity of lax connective tissue which inter venes between it and the posterior cervical wall (fig. 433, G). The membrane, however, still descends, covering first the posterior wall of the supra-vaginal portion of the cervix, and then a part of the fornix, or upper end of the vagina. The extent of peritoneal covering which the vagina receives, varies in different subjects from half an inch to nearly an inch. The membrane then, as before, turns upwards, but at a more obtuse angle, to invest the rec tum, so that a pouch is formed, termed the recto-vaginal or retro-uterine pouch, which is sometimes of considerable size.