Source of the menstrual fink:L.—The vagina, the os and cervix, and the body of the uterus, have been severally reg,arded as the parts which furnish the menstrual flux. Anti so far as the mucous element is concerned it is probable that all these surfaces contribute a certain proportion ; but that the blood in nor mal menstruation is derived mainly from the lining membrane of the body of the uterus, is placed almost beyond doubt by the following considerations :— 1. In the uterus of one who has died whilst menstruating, a remarkable difference is usu ally perceptible in the condition of the mu cous membrane lining the cavity of the body and cervix respectively. That of the body is highly injected, of a deep red colour, the ves sels distinct, and the capillaries numerous. That of the cervix exhibits a condition the opposite of this. It is pale, uninjected, and free from all appearance of distended vessels.
2. If such a uterus be injected, the same conditions are observed in a more marked degree. All the capillaries on the mucous membrane of the body are filled, but compa ratively few of the cervix ; an abrupt line of demarcation occurring sometimes at the internal os uteri.
3. If gentle pressure be employed, as by taking the uterus in the palm of the hand, and slightly approximating the two sides, blood is perceived to flow up from the little pores or orifices of the utricular glands, which are everywhere perceptible, upon the surface of the mucous membrane, until this collects in the cavity in a quantity sufficient to cover the surface.
4. If the same experiment be made under water, in a dish or shallow basin, with the aid of very gentle pressure on the sides of the uterus, such as could not apparently cause any rupture of uterine vessels, the little streamlets of blood are seen welling up from each pore, and mingling with the water. In neither of these cases is the blood seen to proceed from any part of the cemix, but only from the lining membrane of the uterine cavity.
5. The blood, in ordinary menstruation, is seen to flow from the os uteri into the specu lum, but is never observed to proceed froni the lips of the cervix, except the latter be in an abnormal state.* 6. The cavity of the uterus, after death during menstruation, has been frequently, found to contain blood or a coagulum.
From these observations it may he con cluded, that in normal menstruation the blood is furnished by the walls of the uterine cavity. Whether the lining membrane of the oviducts also contributes any portion of the fluid is not certainly known. But I have had reason to think this very probable, from observing that, in cases of death during menstruation, the tubes as well as the uterus contained blood, m hich may in some cases, however, have entered them by regurgitation from the latter. (See also p. 618.) By what means does the blood escape from the uterine vessels in healthy menstruation?— The investigation of this question is attended by great difficulties, and data sufficient even for its approximate determination are yet wanting.
The explanations which have been offered are chiefly the following : — (a.) The blood is supposed to escape in the form of a secretion.
So long as it was maintained that the men strual fluid differed essentially from pure blood, the view that it was eliminated from the general circulatino. current by- a process
analogous to that which obtains in true secret ing glands received ready acceptance, and the inenstrual fluid was, in accordance with such views, denominated a secretion. But since it is now known with tolerable accuracy to what portion alone of the menstrual fluid the term secretion can, with any degree of truth, be applied, it seems useless further to argue the question of secretion or non-secretion, in reference to the main ingredient of this fluid, which has already been shown to be pure blood, unaltered in its physical and chemical constituents, until after it has become mixed with other and adventitious matters.
(b.) The blood is supposed to escape by transudation through the capillaries of the uterine mucous membrane.
This view, which is proposed by Coste and others, need not be considered specially with reference to the uterus. Those who think that the blood-corpuscles, which mi croscopic examination proves to be abun dantly present in the menstrual fluid, can pass by transudation, unaltered and entire, through the walls of capillary or other vessels without rupture of their coats, will find no difficulty in applyin,g this explanation to the production of a like phenomenon, as it rnay be supposed to occur in the uterus.
(c.) The blood is supposed to escape through lacerated capillary vessels.
Many observed facts give to this view a cer tain amount of probability-. Thus, in an in jected uterus the capillary vessels, which form so fine a network upon its inner surface (fig. 439.), may be occasionally observed de nuded, and banging forth in detached loops. In such a condition I have found the vessels when death has occurred during menstrua tion,f Unless this is a post-inortem change, which is improbable, it may be assumed that this laying bare of the capillaries is the conse quence of a vital action, whereby a portion of the epithelial and mucous surfaces are broken down, and subsequently discharged, along with the menstrual fluid. According to the observa tions of Pouchet*, such an exfoliation of ute rine epithelium takes place monthly in women and the mammalia generally. Pouchet, indeed, maintains that not only is there a monthly desquamation from the uterus, but that this extends to the separation and expulsion of a deciduous membrane on each occasion, and that this expulsion, which takes place in the form of the broken down elements of the deciduous lining of the uterus, constitutes the process described by him tinder the title of intermenstruation. Such an exfoliation, if it extended only to the epithelial cells sur rounding the uterine capillaries, would simply leave them bare, but if proceeding to the ex tent of removing the whole deciduous uterine lining, would of necessity carry off with it the whole capillary network of vessels, (see fig. 539.) lying upon the face of this membrane, and consequently would leave a surface of torn capillaries, fronl which the hwmorrhage might occur t, and this in fact takes place in cases when dysmenorrhceal membranes are discharged (fig. 443.).