176 



the deep euds of the glands are driven away from the epithelium 

 aud pushed back against the muscularis. I have observed brown, 

 iron-containing granules iu the connective tissue cells between 

 these glands and also, which is perhaps remarkable, in the epi- 

 thelium of the glands themselves. 



d.) Talpa. 



The placenta of the Mole is discoidal and anti-mesometric. There 

 is an area vasculosa on the yolk-sac, which is subsequently dis- 

 placed by the growth of the allantois. It deserves to be mentioned 

 that at birth only the allantoic villi are shed; the rem aiu der of the 

 placental structures remain behind in the uterus, and are absorbed 

 there. This arrangement Hubrecht has termed 'eontra-deciduate'. 



Strahl states very positively that although the uterine epithe- 

 lium becomes very thin it does not degenerate, but persists as 

 a layer, not always distinctly recognisable, over the ectoderm 

 of the 'villi'. In the fully formed placenta the villi consists of 

 1) the capillaries of the allantois covered by 2) the ectoderm, 

 covered again by 3) a layer derived from the uterine epithelium. 

 This layer, according to Strahl is always quite distinct from the 

 vascular connective tissue of the uterus in which the villi are 

 deeply imbedded. The placenta, therefore, arises by the mutual 

 interdigitation of maternal and foetal constituents. 



The glands in the placental region seem to disappear; opposite 

 their mouths the ectoderm (trophoblast) is columnar, and ingests 

 extravasated maternal blood corpuscles. Instead of penetrating the 

 uterine tissue here the ectoderm bulges out in the opposite direct- 

 ion, forming little 'chorion-blasen'. 



The 'omphalochorion' (omphaloidean trophoblast) is closely 

 attached to the uterine epithelium on the mesometric side; here. 

 Strahl freely admits, this epithelium degenerates. 



Vernhout is equally positive that the uterine epithelium dis- 

 appears in the placental region. According to him Strahl's second 

 layer covering the villi is merely a plasmodial sheet of tropho- 

 blast lining lacunae in which maternal blood is circulating; and 

 the placenta arises, not by the continued ingrowth of 'villi' covered 



