The membranes of the ovum may undoubtedly become the seat of hemorrhage and inflammation at a very early period of pregnancy; these affections are probably the cause of the formation of moles, but they may also give rise to abortion. The dirty white and ash-colored spots occurring in various sizes upon the amnion, and accompanied by thickening of the membranes, and the opacity sometimes affecting the greater part of the amnion, evidence previous inflammation. But under this head we must more particularly instance the deposits of a grayish-red, whitish, or yellowish substance, occurring on the chorion and the decidua, in the shape of patches. The membranes here present a thickening without distinct edges, or flattened rounded nodules; the tissues being either softened and friable, or indurated and dense. Occasionally the membranes, in consequence of a cretification of the deposit, are incrusted, or contain a chalky grit.

The albuminoid layer which represents the so-called tunica media, is not unfrequently morbidly increased in quantity; sometimes a thin, brawny, or watery accumulation is substituted for it, and to the latter the discharge of the so-called spurious liquor amnii in the second half of pregnancy, is probably due (hydrallantois). In other cases its amount is very small, or it presents greater consistency, and may even be tough and membranous.

The villi of the chorion degenerate at an early period of pregnancy, into pedunculated vesicles or cysts, which are placed at their extremities; a degeneration which is also seen in the placenta; when occurring in an extensive and advanced degree they represent what has been termed the vesicular or hydatid mole.

Occasionally we discover more or less extensive adhesions between the embryo and the amnion, which is a circumstance of some importance, on account of the impediment it offers to the proper development of the foetus.

The liquor amnii is sometimes so much reduced in quantity, that the foetus is closely invested by the amnion, at others it is excessive (hydram-nios); it is also found more or less opaque, discolored, and fetid.