THE CH ORION WITH TROPHODERM. 



nected with one villus is fused with that of adjacent villi, the whole constituting 

 a large irregular mass of cells, Tro, the trophoderm. In many places it has 

 already disappeared, so that there are spaces, lac, in the trophoblastic mass. On 

 the edges of these spaces the trophoblast is undergoing degeneration, deg, and 

 where that is occurring it is marked in the figure by the deeper staining of the 

 degenerated material. Upon examination with a higher power (Fig. 243) it will 

 be noted that the mesodermic cells are stained much more deeply than the matrix. 



ntes. 



EC. 



lac. 



Tro. 



FIG. 242. SECTION OF A VERY YOUNG HUMAN CHORION. 



deg, Degenerating ectoderm. EC, Epithelial ectoderm, lac, Lacuna for maternal blood, mes, Mesoderm. Tro, 



Trophoderm. Vi, Villi.- X 50 diams. 



They hav.e an elongated form and run in various directions, more or less parallel 

 to the epithelium, EC'. Many of them are cut transversely or obliquely. Aside 

 from the trophoderm, the ectoderm is everywhere two-layered. The inner layer 

 is distinctly cellular, the outlines of the cells being very sharply marked and the 

 nuclei being relatively large. In the. outer layer, which is stained more darkly, 

 there are no cell boundaries to be recognized, the structure being syncytial. The 

 nuclei are smaller and more deeply stained than those of the inner layer. In 



