232 THE FEMALE REPRODUCTIVE SYSTEM 



is filled and the decidiia capsularis fuses with the decidua vera. 

 At birth, the amnion sac is usually torn open, the contained liquid 

 flows down into the vagina, and the young is expelled by the power- 

 ful contractions of the hypertrophied myometrium of the uterine 

 wall aided }\y contraction of the abdominal skeletal muscles. After 

 the young emerges there is an after-birth. This consists in the 

 exiDulsion of the amnion and the deciduse, together with a consider- 

 able superficial portion of the hypertrophied uterine mucosa. This 

 process involves considerable hemorrhage in case of intimate rela- 

 tionship between the chorionic villi and the uterine mucosa. After 

 the birth process is completed, the hemorrhage usually ceases and 

 there is a slow and gradual regeneration of the uterine mucosa, 

 returning to a condition similar to that found in an ordinary inter- 

 menstrual, or resting period. 



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 CoNEL, J. L. 1931. The genital system of the Myxinoidea: A study based 



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628. 

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