Accordin,,,, to my observations the contrac tile fibre-cells are not distributed in equal pro portions through all parts of the muscular coat, nor are they found everywhere in the same condition. It has been already. stated, that no strict line of demarcation is discern ible by the microscope between the three several coats, of which the uterus is said to consist. And this is particularly the case in respect of the muscular fibres which permeate all of them. In the so-called mucous meni brane the muscular fibre-cells are loosely ar ranged in an amorphous tissue, in which they lie embedded. intermixed with the elementary nuclear corpuscles, constituting their embry onic condition. Here the fibre-cells form bundles, situated between the ramified canals or utricular glands of the uterus, and take a direction more or less oblique or perpendicular with regard to the inner uterine surface. But at the level of the base of the uterine follicles, where the proper muscular coat is considered to begin, and the mucous membrane to termi nate, the contractile fibre-rells assume a dif ferent direction and arrangement. Here at once they. begin to exhibit a certain order of stratification, the strata being very closely su perimposed, and arranged for the most part in such a manner as to lie parallel with the walls of the uterine cavity, which is therefore sur rounded by them.
These strata exhibit certain differences of composition and arrangement sufficient, for the sake of description at least, to justify an artificial division of them into three orders.
The innerm.ist of these may be termed the dense muscular strata. They commence im mediately external to the inncous membrane, and extend outwardly through about half or two thirds of the thickness of the muscular coat.
When preparations that have been preserved in weak spirit, or those that have been finely injected, are examined by the naked ey e, or with a hand lens, a peculiar mottled appear ance is presented by sections of this part, caused by the intermixture of numerous mi nute white lines ramifying within a darker substance, and dwitling it into a multitude of small lozenge-shaped spaces. The whiter lines niark the course of the finer uterine vessels, together with the bundles of white fibrous tissue which accompany them. The browner lozenge-shaped spaces consist of the fusiform contractile fibre-cells, united together by amorphous tissue into short bundles, which by their superposition constitute the lamina: just inentioned. When horizontal sections are made of this portion of the muscular coat, such as are represented in fig. 428., these bundles or strata are seen to be arranged in a concentric manner, forming interrupted circles surrounding the uterine cavity. But this ap
pearance must not be regarded as indicative of any corresponding direction of the muscu lar fibre-cells. within these bundles or !mi nce, for all appearance of a concentric plan, as regards the fibres, at once vanishes under the use of the microscope.
Fig. 436., representing a fine section tp.ken from the inner muscular laminm, serves to exhibit the mode in which the contractile fibre-cells are arranged in this portion of the uterine walls. The individual fibres and em bryonic corpuscles are imbedded in an amor phous substance (the unformed connective tissue already described), by which they are aggregated together, so as to form bundles and laminm. In these strata the fibre-cells appear to remain distinct, and to be separated from each other by a distance not greater usually' than their own diameters.
This is best shown in fine sections, pre viously prepared by acetic acid ; but it should be observed, that as this agent causes the intermediate tissue to swell, the normal tances between the cells may, to a certain extent, be thus artificially increased. The relation of the fibre-cells to the uniting ma terial is most clearly exhibited in those parts of the preparation where the knife has divided the fibres transversely to their long axes. Here the relation of these two structures to each other may be exemplified by that of the harder and softer ingredients in certain por tions of those geological formations termed conglomerate.
At the points where the knife has cut the fibres obliquely, a corresponding change is observable in the outlines of the divided fibre cells, which present in these bundles the figure of caudate cells, while in other places, where the course of the fibres has run paral lel with the surface of the section, the fusi tbrm outline of the entire length of the fibre is distinguishable.
All these varieties of direction are notice able infig. 436., in a portion of uterine tissue not more than -61u" in diameter. The fibres which are here seen forming bundles and layers, run in some instances parallel with the surfaces of the laminm, and in other places spread out fan-shaped, or incline towards each other, like the component fibrillm of the penniform muscles. The bundles and layers of fibres are close-set and compact, and a comparatively small amount of developed or fibrillated connective tissue is found between or among these elements of the innermost strata of the muscular coat. The fibre-cells also are here apparently softer and more fleshy, and appear to be of newer formation than those forming the layers which lie nearer to the peritoneum.