As to Win Aler's theory of a sub-amniotic capillary plexus, Bar rejects it also.
d. The fluid is a peculiar secretion of the amnion.
The amnion, according to Hotz, is often covered with a layer of cylin drical cells, and B011iker records a case in which there were many am niotic caruncles. Buttheir function is still entirely unknown.
2d. The amniotic fluid is a product of the maternal organism.—Ahlfeld claims that in consequence of the eccentric hypertrophy of the uterus, the pressure upon its contents is less than the abdominal pressure; and since it is a closed cavity, the maternal blood must necessarily flow into it. This negative pressure diminishes progressively up to the third month, when it ceases, the contents thenceforward developing equally with the organ itself. The serosity, in passing from the vessels to the egg, traverses the pores of the chorion and of the amnion, and the author has been able to prove the existence of blood-coloring matter in these pores, which had traversed the chorion and had penetrated to the epithelium of the amnion.
Ikopold agrees with Ahlfeld so far as the first months of pregnancy are concerned; and Zuntz, whose experiments have proved that substances injected into the maternal vessels may pass into the liquor amnii without going through the body of the fcetus, believes that, at least in part, the liquor amnii is derived from the maternal blood. Wiener and Bar have repeated Zuntz's experiments, and have arrived at the same conclusions.
3d. The fluid is derived both from the mother and from the child.— This is Virchow 's opinion; he holds that the fcetal portion is composed of the vernix caseosa and renal secretion, the rest being essentially a ma ternal transudation.
As we see, theories are not wanting; but the real cause of dropsy of the amnion remains to be found. Whether we admit that the liquor amnii comes from the mother, or whether we believe, as the more probable. supposition, that it is produced by the fo3tus and the membranes, it in no way explains the occurrence of dropsy of the amnion. The following facts are to-day incontestible, and have been proved by various observa tions.
lst. Dropsy of the amnion coincides very frequently with twin preg nancy.
2d. Children born with the complication of dropsy of the amnion are often the subjects of malformations and monstrosities.
3d. A certain number of women who have dropsy of the amnion are syphilitic, and their children, born dead or living, show unmistakable signs of the disease. Finally hydramnion is very rare in primiparie, and seems to be especially liable to occur after a certain number of preg nancies.
Mac Clintock, in 33 cases, found primipara3 5; second pregnancies 8; third to twelfth pregnancies 20.
As to twin pregnancies, the following figures will suffice: In the 114 children, 1 of which was a case of extra-uterine pregnancy, there were: girls, 23; boys, 38; unknown, 53.
Can we explain the coincidence of dropsy of the amnion with twin pregnancy? Is it exaggerated uterine development, or the stretching of the membranes, or compression of one fcetus by the other, or is there anything peculiar about the circulation or the blood pressure, or in the arrangement of the placenta and membranes that accounts for it ? It is impossible to say. We know that there may be one of four oonditions present in these twin births: lit. A single placenta, chorion, and amnion, with a communication between the two ftvtal circulations.
2d. A single placenta, chorion and amnion, with an almost constant communication between the two circulations; or one chorion and two amnions, with a rarer communication.
3d. Two isolated placenta3, united by a membranous bridge; rarely communication between the two circulations; often two chorions and two amn ions.
4th. Two entirely distinct placents3, two chorions and two amnions; no communication between the two circulations.
Frankenhauser only seems disposed to admit hydramnion as' possible in cases where there exists a communication between the two fcetal circula tions. In consequence, he claims that the e,ardiac activity of the stronger fcetus causes cardiac stasis in the weaker one, and hence increased trans udation on that side. Schatz agrees with this opinion, and says: " The child that has the more powerful beart will have the greater arterial pres sure, will secrete more urine, and have more liquor amnii." To this Sal linger rightly objects that in that case we should have hydramnion in twin pregnancy with an acardiac fcetus; whereas this has not been found.