. Quain's elements of anatomy . acenta, thus including a placental and a uterinedecidua serotina. Fig. 673. Fig. 673. — Semi-diagram- matic OUTLINE OF ANANTEEO-POSTERIOR SECTIONOP THE GRAVID UTERUS■AND OVUM OF FIVE -WEEKS (). This drawing is taken froma very perfect specimen ofthe uterus obtained from tliebody of a woman who died ofcholera in 1849. a, anterior uterine wall in-side which was situated theplacental attachment of theovum; p, posterior uterinewall (the accessory parts beingomitted) ; m, muscular sub-stance of the wall; r,thickened lining membraneforming decidua vera, andshowing
. Quain's elements of anatomy . acenta, thus including a placental and a uterinedecidua serotina. Fig. 673. Fig. 673. — Semi-diagram- matic OUTLINE OF ANANTEEO-POSTERIOR SECTIONOP THE GRAVID UTERUS■AND OVUM OF FIVE -WEEKS (). This drawing is taken froma very perfect specimen ofthe uterus obtained from tliebody of a woman who died ofcholera in 1849. a, anterior uterine wall in-side which was situated theplacental attachment of theovum; p, posterior uterinewall (the accessory parts beingomitted) ; m, muscular sub-stance of the wall; r,thickened lining membraneforming decidua vera, andshowing grooves and emi-nences on its surface andenlarged glands and vesselsin its substance ; g, the glan-dular or deep layer ; r, thedecidua reflexa; u, indicatesthe uterine cavity ; s, deciduaserotina; c, cavity of thecervix uteri; cJi, chorion withits villi, which are morehighly developed on the pla-cental side; e, the embryoenclosed in the amnion, withthe allantoic vessels passing into the placenta, and the umbilical The blood-vessels and the glands of the mucous membrane also un-dergo great enlargement and modification. The whole of the decidua veraand the adjoining part of the reflexa are at first penetrated by blood-vessels derived from those of the uterus, more especially in the latter partof the second month, when the decidual structure may be considered ashaving reached its highest degree of development. After this time theblood-vessels of the decidua reflexa, and later those of the whole liningdecidua of the uterus, except in the immediate vicinity of the placenta,shrink and ultimately disappear, so that the membrane formed by theunited decidu^e becomes in the end wholly non-vascular. The same retro-grade process, leading to atrophy and disappearance, occurs in the blood-vessels of the chorionic villi by which the decidua reflexa is penetrated,and, although the viUi themselves never entirely disappear, but may be THE PLACENTA. 779 Fig. 674. traced even in the
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