PLATE II. 
Fig. 2. Section Through the Blastocyst and Implantation Cavity. Photograph at a magni¬ 
fication of 85 d. D , on the free surface of the decidua, indicates a hollow corresponding 
to the dimple in the figure on page 10. The appearance of a dimple on the surface 
is due to the relative thinness of the decidual wall of the implantation cavity directly 
over the blastocyst. It does not correspond to the point of entrance, which lies nearer 
the left margin of the lobule (see Plate III, Fig. 3). The section shows the decidual 
wall of the implantation cavity ; the darker band represents the necrotic zone of the 
decidua. The blastocyst is at this point somewhat folded and irregular. Its interior 
is filled with mesoblast, and in the centre is a cavity of retraction in which a portion of 
the torn amnio-embryonic vesicle is seen. The cyto-trophoblast can be made out and 
the plasmodi-troplioblast here forms a very irregular reticular formation, more especially 
at one end, below in the section. Above this is a considerable mass of effused blood 
which has partly torn up the formation, in part pressed it down on the cyto-trophoblast. 
Within the necrotic layer of the decidua, especially below and to the left, a lamella of 
large free cells is seen. The decidua is crowded with leucocytes. 
