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the amniotic cavity bas now appeared. Mesometrically it extends 

 upwards towards the uterine lumen from the walls of which the 

 epithelium is now disappearing; aud before very long lacunae are 

 formed in the uppermost portion of it, in which blood, extra- 

 vasated froui the ruptured subepithelial vessels, soon circulates. 

 In this lacuuar portion the cell bonndaries rapidly become in- 

 distinct, and to it the terms trophoblastic syncytium, plasmod- 

 iblast, or plasmoditrophoblast have been applied in contradistinction 

 to cytoblast, or cytotrophoblast, the name used to designate the 

 lower cellular part which is at present united with the aranion; 

 but it must not be forgotten that cell boundaries will later on 

 reappear in the upper portion of the trophoblast immediately 

 adjacent to the maternal tissues. Laterally of course the allan- 

 toidean trophoblast passes into the omphaloidean, and here the 

 trophoblastic cells are transformed into megalokaryocytes which 

 have the same structure and behave in the same way as those 

 above described in the latter region. In the centre however the 

 trophoblastic cells (as we may for the sake of convenience term 

 the cytoplasmic areas surrounding the nuclei in the syncytium) 

 although they enlarge very considerably do not attain the enormous 

 dimensions of the megalokaryocytes. These cells too are phago- 

 cytic; enclosed in food vacuoles inside them may be seen red 

 blood corpuscles, siugly, or in clumps, leucocytes, and the débris 

 of epithelial and other cells (Figs. 22, 28). The nuclei of this 

 cellular débris show marked signs of degeneration; they stain 

 strongly; they contain coarse irregular masses of chromatin, which 

 are often scattered through the cytoplasm by the breaking up of 

 the nucleus, or the nucleus may itself be extruded from the cells. 

 As for the cytoplasm, it stains brilliantly with plasma stains and 

 offers in this respect a marked contrast to the cytoplasm of the 

 trophoblast by which it has been ingested. In the latter there are, 

 besides the ingested material, numerous small granules of variable 

 size, staining brilliantly with acid stains, which appear to be of 

 the same nature, whatever that may be, as are the similar gra- 

 nules of the megalokaryocytes. 



