CHAPTER XII. 



DISCHARGE OF THE F<ETUS JLJVD PLACENTA. 

 ERATION OF THE UTERINE TISSUES. 



REGEN- 



DURIXGr the growth of the embryo, and the development of the 

 placenta, the muscular tissue of the uterus increases in thickness, 

 while the whole organ enlarges, to accommodate the greater volume 

 of its contents. This unusual growth of the muscular tissue gives it 

 an increased contractile power sufficient for the expulsion of the foetus 

 at the time of delivery. 



The enlargement of the amniotic cavity, and the greater abundance 

 of the amniotic fluid, provide space for the intra-uterine movements 

 of the foetus. These movements begin to be perceptible about the fifth 

 month, at which time the muscular system is sufficiently developed to 

 show a certain amount of activity. During the latter months of preg- 

 nancy they become more frequent and vigorous, and may often be felt 

 by the hand of the observer applied over the region of the uterus. 



The attachment of the embryo to the investing membrane of the 

 egg is at first by a short and wide funnel-shaped connection, consisting 

 of the commencement of the 

 chorion, a part of the amnion, 

 and a deposit of gelatinous ma- 

 terial between the two, contain- 

 ing the stem of the umbilical 

 v< i >ide. Subsequently, as the 

 amniotic cavity enlarges, the 

 body of the embryo recedes from 

 the inner surface of the chorion, 

 by the elongation of its connect- 

 ing part; and this, part conse- 

 quently begins to present the 

 appearance of a cord (Fig. 212). 

 It is still surrounded with a thick 



layer of gelatinous matter, by HUMAN EKBRYO AKD ITS MEMBRANES, in the 

 which it is Separated from its earl 7 period of gestation ; showing the forma- 



amniotic investment. As it tion of the umbuical cord - 

 emerges from the embryo, at a point where the abdominal walls will 

 afterward close round it, to form the umbilicus, it is known by the 

 name of the umbilical cord. It contains the blood-vessels passing out 

 to the chorion and placenta. 



After the third month the umbilical cord and its blood-vessels elon- 

 gate more rapidly than is required by the increased size of the amniotic 



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