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end of the embryo ; this is the ectoplacenta, and its outer 

 layer is plasmodial. 



The uterine sub-mucosa thickens, becomes folded ; two 

 of the folds are the placental lobes, of loose connective 

 tissue with blood capillaries. The epithelium of the lobes 

 is deeply pitted (uterine crypts) to form branched glands. 

 The ectoplacental plasmodium forms irregular processes, 

 which firmly fuse with the surface of the placental lobes ; 

 and the glandular epithelium of the lobes then degenerates 

 and disappears. As the ectoplacental processes burrow 

 in, they come into close contact with the dilated sinus-like 

 uterine capillaries and destroy their walls. Simultaneously, 

 mesoblast of somatopleure grows in betAveen folds formed 

 on the lower surface of the ectoplacenta. 



Meanwhile the allantois has spread rapidly between the 

 amnion folds, and over the back of the embryo ; and its 

 outer (mesoblast) wall fuses with the mesoblast of the 

 false amnion beneath the ectoplacenta. In that way the 

 allantoic blood-vessels are brought into close relation with 

 the uterine sinus-like capillaries. The folds of mesoblast 

 containing the vessels deeply invade the ectoplacenta, 

 cutting it up into columns ; there is an interlocking of 

 foetal with maternal vessels, and only thin endothelium 

 is left between these when the ectoplacental plasmodium 

 is finally absorbed. The true (allantoic) placenta, thus 

 formed, is the organ by which the developing embryo breathes 

 and is nourished; and its formation is partly maternal 

 (deciduous portion of sub-mucosa of uterus), partly foetal 

 (ectoplacenta portion of false amnion, and the nutritive 

 and respiratory allantois). 



Parturition : The placenta of the Rabbit is deciduate, 

 i.e., the maternal portion (decidua) as well as the foetal 

 portion comes away with the young at birth. The separa- 

 tion is brought about by strong contractions of the uterine 

 muscles. 



What is the Umbilical Cord ? 



The cord-like portion of the placenta issuing from the 

 umbilicus or navel of the foetus ; and consisting of the yolk- 

 sac stalk and the corresponding portion of the allantois 

 with vessels, and within an amniotic sheath. 



