The theory of menstruation in early pregnancy, superfœtation and the site of insertion of the ovum / by J. Matthews Duncan.

Date:
[1853]
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Licence: Public Domain Mark

Credit: The theory of menstruation in early pregnancy, superfœtation and the site of insertion of the ovum / by J. Matthews Duncan. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    illustrations. But the dissection above described shows that the uterus is not closed up till sometime about the third month, and there is no reason to think superfcetation impossible till this takes place.1 The uterus does not become closed, and repeated impregna- tion is not impossible, till the ovum is so large as to force the decidua reflexa into close and firm opposition to the decidua vera. Up till this time (in the third month) there is a sufficiently free commu- nication between the ovary and the vagina, or between the ova and the semen. In the uterus described, there is at least as much free space for this communication, as exists in the long and very contracted cervical passage of the virgin uterus. Numerous phy- siologists adduce the plug of viscid cervical mucus as an impedi- ment to impregnation during pregnancy; but frequent examina- tions have convinced me that this plug is dense and well developed, and apparently impassable in the non-menstruating unimpregnated uterus, and as it does not prevent conception then, so there is no reason to ascribe to it this function in early pregnancy. Without taking up space in going over the numerous cases of superfcetation which are everywhere recorded, it may be stated that this explanation will account for all the authentic cases. For if we suppose in an instance of this kind, that the first child is born pre- maturely, but within the limits of viability, we thus gain two months; and if impregnation may take place between two and three months after conception, we have thus four or five months of in- terval accounted for between the births of successive viable infants. In the same way it is easy to explain the difference in apparent age and development often observed in twin-births; which may thus be instances not unfrequently of superfcetation with this peculiarity, that both children, though conceived at different times, are born at or near the same time.2 The dissection above described, and numerous others, have de- monstrated that the decidua is formed by the development of the normal mucous membrane of the uterus, without closing the tubes or cervix uteri. The only new production is the compara- tively thin uniform membrane of the decidua reflexa, which springs 1 It is now established, chiefly by the researches of Pouchet, Raciborski, and Bischoff, that a mature ovum is ordinarily expelled after every menstrual period. On the occurrence of pregnancy, the maturation of ova in the Graafian vesicles, and their expulsion, are generally arrested till the end of the period of suckling. But this is not invariably the case. In the human female the sign of ovula- tion being about to take place is the occurrence of menstruation. The dis- charge of the menstrual fluid necessarily displaces the mucous plug in the cervix of the pregnant as of the unimpregnated uterus, and thus clears a passage for the conjunction of the ovum of the female with the spermatozoon of the male. 2 I may state that all such cases cannot be explained by the supposition of superfcetation. Most conclusive evidence to this effect is afforded by a prepara- tion in my collection of a double monster (anterior duplicity), in which the foetuses differ considerably in size; and it is difficult to conceive that superfcetation has anything to do with the anomaly of double monstrosity.