These several tissues are arranged in a manner not materially different from the plan already described as observable in the body of the uterus. But the thin external strata which form the tegumental layers of the body are wanting in the cervix. There may, how ever, be distinguished an outer and more vascular, and an inner and more dense series of laminm. The laminm of the outer series are intermingled with numerous divisions of the cervical branches of the uterine vessels which traverse them obliquely in a direction from above downwards and from without in wards. From the abundance of these vessels the external laminm present a more spongy appearance, and when the part has been in jected a much deeper colour than the inner layers, which are paler, more dense and closely set, and exhibit at the same time fewer sections of' vessels, and these only of the finer kind. The large amount of white fibrous tissue, and the density and compact ness of the larninm here forined around the cervical canal, give to clean sections of this part an appearance of circles concentrically arranged. But a low magnifying power is sufficient to resolve these into the lozenge shaped spaces already described, consisting of bundles of contractile fibre cells bordered by fibrous tissue, and intermingled with bun dles of the latter and blood-vessels of various sizes. Within these laminm and bundles the fibres take their course with as many varia tions in direction and plan of arrangement as are noticeable in the muscular fibres of the rest of the uterus. (Seefig. 436.) The larger proportion of tbe fibrous ele ment in the neck as compared with the body of the uterus, which the microscope serves to display, and which to a certain extent is ob servable to the naked eye, may be more satis factorily shown by the operation of dilute acetic acid ; this agent causing thin sections of the part rapidly to swell out and assume a gelatinous appearance.
Mucous coat of the cervix.— This is com posed of epithelium, basement membrane, and the usual fibrous and vascular tissues, together with certain papillm and follicles. It is of a more dense and uniform texture upon the outer or vaginal portion of the cervix than within the canal, where it is more delicate, but being here thrown into nume rous folds and rugm, an appearance is given of greater thickness than the membrane really possesses. The average thickness of the mucous membrane upon the lips of the cervix is +— if"'; that of the membrane with in the cervical canal, regardless of the folds, is somewhat less. The general plan of ar rangement, and some of the more prominent forms which this membrane assumes within the cervical canal having been already con sidered, it only remains here to describe the minuter structures of which it consists.
The epithelium of the outer or vaginal por tion of the cervix is tessellated or squamous. It gives a smooth and even covering to the two lips of which this part of the cervix con sists. Outwardly, this scaly epithelium is continuous with that of the vagina, but to wards the os uteri it terminates at the margin of either lip. Within the cervical canal the
epithelium changes its form. It has been desrtibed here a.s constantly cylindrical or dentate ; but upon all the finer structures here found, such as the filiform papillm, this so-called epithelial covering consists, as Reichert has well described, and Kilian ac curately represented it, of elemental-) cells, whose cell meinbranes are closely united to gether, having a polyhedral outline, and AV ith out undergoing such an amount of flattening as to lose their spherical form. They contain a slightly flattened nucleus with several nu cleoli, surrounded by a clear somewhat thick fluid intermixed with molecular bodies, and sometimes oil globules.
Some difference of opinion exists as to the part of the cervical canal in which the epithe lium first becomes ciliated. Drs. Tyler Smith, and Hassall, who have examined numerous uteri at an early period after death, with a view to anticipate post-mortem changes, state that the ciliation of the epithelium commences in the rugose portion of the canal, and ex tends up to the fundus, while the epithelium just within the os, though also cylindrical, is not ciliated.* It should be observed, however, that there is no particular portion of the cer vical canal in which the membrane constantly becornes rugose, but that the rugosities often extend quite down to the margin of the os. According to Henle t, the cervix is provided with ciliated epithelium from the middle up wards, and with pavement epithelium from that point downwards.
One peculiarity or variety in the arrange ment of the epithelium upon the vaginal por tion of the cervix requires special notice here on account of the singular degree of import ance which has of late years been attached to it, and still more from the remarkable pa thological speculations to which it has given rise.
It occasionally happens that the tessellated epithelium of this part, instead of extending as far as the os, abruptly' ceases at a distance of one or two lines from the inner margin of either or both lips, leaving a single or double crescentic patch where the ordinary pave ment epithelium is replaced by' a crop of close set filiform papillze, projecting very slightly, if at all, above the general surface, and pre senting to the touch that velvety feel, and to the eye, on account of their great vascularity, that florid aspect, which has often led to the supposition that this mere morphological va riety of structure is the result of a pathologi cal change, and that it constitutes a form of ulcer peculiar to the os uteri.
Beneath the epithelium is a basement niem brane, which, upon the outer portion of the cervix, extends in a smooth lamina over the papillm that everywhere crowd this part, but within the cervical canal it dips into the furrows and follicles, or covers its numerous rugosities and projections.