766 DISCHARGE OF FCETUS AND PLACENTA. 



produced upon the mother by such a hemorrhage, because the propor- 

 tion of blood in the rest of the vascular system remains the same. 

 Uterine hemorrhage at the time of delivery becomes injurious only 

 when it continues after complete separation of the placenta ; in which 

 case it is supplied by the mouths of the uterine vessels, left open by 

 failure of the uterine contractions. These vessels, in natural parturi- 

 tion, are instantly closed, after separation of the placenta, by the con- 

 traction of the uterine muscular fibres. They pass, as already men- 

 tioned, in an exceedingly oblique direction, from the uterus to the 

 placenta; and the muscular fibres, which cross them transversely above 

 and below, necessarily close their orifices by constriction as soon as 

 they are thrown into a state of functional activity 



Regeneration of the Uterine Tissues after Delivery. Both the mu- 

 cous membrane and muscular tissue of the uterus, which are the seat 

 of an unusual growth during pregnancy, are afterward replaced by 

 corresponding tissues of new formation. The mucous membrane, or 

 decidua, is discharged at the time of delivery ; and the hypertrophied 

 muscular tissue, which has served its purpose in the expulsion of the 

 foetus, undergoes soon afterward a process of retrogression and atrophy. 



A remarkable phenomenon connected with the renovation of the ute- 

 rine tissues, is the appearance in the uterus, during pregnancy, of a 

 new mucous membrane, growing underneath the old, and ready to take 

 the place of the latter after its discharge. 



If the internal surface of the body of the uterus be examined imme- 

 diately after parturition, it will be seen that at the spot where the pla- 

 centa was attached, every trace of mucous membrane has disappeared. 

 The muscular fibres of the uterus are here exposed and bare ; while the 

 mouths of the ruptured uterine sinuses are also visible, with their thin 

 edges hanging into the cavity of the uterus, and their orifices plugged 

 with bloody coagula. 



Over the rest of the uterine surface the decidua vera has also disap- 

 peared. Here, however, notwithstanding the loss of the original mucous 

 membrane, the muscular fibres are not perfectly bare, but re covered 

 with a semi-transparent film, of whitish color and soft consistency. 

 This film is an imperfect mucous membrane of new formation, which 

 begins to be produced, underneath the old decidua vera, as early as 

 the beginning of the eighth month. We have seen this very dis- 

 tinctly in the uterus of a woman who died undelivered at the above 

 period. The old mucous membrane, or decidua vera, is at this time 

 somewhat opaque, and of a slightly yellowish color, owing to partial 

 fatty degeneration. It is easily separated from the subjacent parts, 

 on account of the atrophy of its vascular connections ; and the new 

 mucous membrane, situated beneath it, is distinguishable by its fresh 

 color and semi-transparent aspect. 



The mucous membrane of the cervix uteri, which takes no part in 

 the formation of the decidua, is not thrown off in parturition ; and after 



