THE AFTER-BIRTH. 



55 



Fig. 64. 



Artery 



Artery 



Vein 



Transverse section ot umbilical cord at end of pregnancy, 

 taken from placental end; the umbilical blood-vessels are em- 

 bedded within the embryonal connective tissue. X 10. 



While the attachment of the cord usually is situated near the middle of the 

 placenta, it is seldom exactly central ; the insertion is subject to great variation, 

 however, the eccentricity sometimes being so great that the cord is fixed to the 

 periphery of the placenta, such disposition constituting insertio jnarginalis. Among 

 the more exceptional variations in the arrangement of the cord are the cleft and the 

 extraplacental attachment known respectively as insertio furcata and insertio vela- 

 me?itosa. In the former condition, where the cord divides before reaching the pla- 

 centa, each limb conveys one of the umbilical arteries and a branch of the umbilical 

 vein. When the insertion of the 

 cord is into the chorion entirely 

 outside the placental area, in ex- 

 ceptional cases being as far re- 

 moved as the opposite pole of the 

 membranous capsule, the umbilical 

 vessels course within the non-vil- 

 lous portions of the chorion until 

 they reach the foetal placenta. In 

 addition to the true knots, which 

 often occur and are due to the 

 excursions of the foetus, the um- 

 bilical cord sometimes presents 

 nodular thickenings and irregular 

 constrictions, as well as projections 

 formed by loops and varicosities of 

 the blood-vessels. 



The After-Birth.— The ex- 

 pulsion of the child through the 

 rupture in the enveloping mem- 

 branes, which is produced by the 

 powerful contractions of the uterine 



muscle at the close of pregnancy, is followed, after a short interval, by the separa- 

 tion and expulsion of the "after-birth ;" under this term are included the placenta 

 and the enveloping membranes. The latter, as will be understood from the fore- 

 going consideration of the encapsulation of the foetus, consist of three chief constit- 

 uents, — the remains of the decidua vera, the chorion, and the amnion ; the reflexa 

 undergoes complete absorption. Since the decidua represents the shed portion of 

 the modified uterine mucosa, the outer surface of the after-birth appears rough and 

 studded with shreds of uterine tissue ; the inner surface of the decidua is so closely 



fused with the adjacent cho- 

 FiG. 65. rion by means of delicate 



connective tissue that only 

 a limited and uncertain 

 separation is possible. The 

 amnion, on the other hand, 

 although attached to the 

 chorion by bands of connec- 

 tive tissue, may be peeled 

 of? the chorion with relative 

 ease, since the union be- 

 tween the two membranes is never firm. The inner ectoblastic surface of the 

 amnion in contact with the foetus is smooth and bathed m the liquor amnii. The 

 external and unshed portion of the modified uterine mucosa contains the incon- 

 spicuous remains of the epithelium lining the fundus cf the glands : these elements 

 are of the utmost importance for the regeneration of the glandular and epithelial 

 tissues of the new uterine mucous membrane, since the reparation of these struc- 

 tures, which is effected within a few weeks after labor, begins in the proliferation of 

 the deeper glandular epithelium, which remains throughout pregnancy as the latent 

 source of subsequent repair. 



Amnion 

 Chorion 



Decidua 

 Remains of 

 titerine glands 



Uterine muscle "^.-n -^x?'*- 



Section through fcetal membranes and uterus at end of pret;natic\. 

 {After Leopold.) 



