The principles and practice of obstetrics . ne cavity. The ovum thusis again united to the mothers tissues. The villi of thechorion, being completely covered with the laminae ofthe decidua, become the only media of connection be-tween the embryo and the maternal tissues. Those who represent the membrana decidua as asimple development of the mucous membrane contendthat the ovum passes into the uterine cavity, where itis arrested by the folds of the mucous membrane. Atthis place the membrane is still more rapidly developed,and soon covers the ovum, so as to constitute a deciduareflexa, as above
The principles and practice of obstetrics . ne cavity. The ovum thusis again united to the mothers tissues. The villi of thechorion, being completely covered with the laminae ofthe decidua, become the only media of connection be-tween the embryo and the maternal tissues. Those who represent the membrana decidua as asimple development of the mucous membrane contendthat the ovum passes into the uterine cavity, where itis arrested by the folds of the mucous membrane. Atthis place the membrane is still more rapidly developed,and soon covers the ovum, so as to constitute a deciduareflexa, as above described, re-establishing the connec-tion between the parent and the child. During the second and third months of gestationother changes will be observed. The embryo will befound floating in the liquor amnii, having no otherattachment to its membranes than that through theumbilical vessels at the place where these vessels aredistributed to the chorion. At this point there is arapid development of the villi, while on the remaining Fig. OvrM of ABui t Five Montus.—a. Portion of Jlcmbrana Decidua. b. Placenta, e. Chorion, d. Amnion containing Foetus. THE PLACENTA. 59 portions of the chorion they gradually disappear. Theenlarged villi, just mentioned, continue to be developed,and are covered with the membrana decidua, withwhich they become most intimately connected, andconstitute the body known as the placenta or after-birth. This body is quite perfect at the third monthof gestation, and continues to augment in proportion tothe development of the foetus until term. On everyother portion of the ovum the membrana decidua di-minishes in size and vascularity, so that at the fullperiod it is exceedingly thin and delicate, the strength of the ovum depending almost exclusively on the cho-rion and amnion. Hence, in the early period of gestation the commu-nication between the child and the parent is main-tained through the medium of the spongioles of thechorion and the membrana deci
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