PLATE III. 
Fig. 3. Section Through Blastocyst and Implantation Cavity at the level of the point of 
entrance, x 100 d. dec., decidua ; n.z., necrotic zone of decidua ; P.E., point of entrance ; 
gl., gland ; bl.v., maternal capillaries : hg., haemorrhage. 
The cavity of the trophoblast is at this point filled with mesoblast. The cyto- 
trophoblast appears as a blue-pink lamella ; the plasmodi-trophoblast as bands and threads of 
protoplasm stained of a dusky-red colour enclosing nuclei. The spaces in the plasmodium 
are occupied by maternal blood corpuscles. These come from maternal capillaries opened 
up as the implantation cavity enlarges. In the upper part of the section there has been 
a considerable haemorrhage into the decidua ; this has in part broken down the necrotic 
zone, and the mass of effused blood has partly torn up the plasmodial bands. The 
implantation cavity is lined by a necrotic zone of the decidua distinguished by its pink 
colour ; the unaltered parts of tlie decidua have a grey-blue tint. Within the necrotic 
zone are seen numbers of free cells. The glands of the decidua are dilated ; their 
epithelium is desquamating, and their lumen contains red and white blood corpuscles. 
The blood-vessels are much dilated, more especially on the deep aspect of the decidua, 
where they form almost sinus-like spaces ; to the right and below, the endothelium of 
one wall of such a vessel is seen covering the decidua. The decidua is crowded with 
leucocytes. The point of entrance shows a depression filled with a mass of fibrin ; 
continuous with this and with the necrotic tissue, a fibrinous spur projects into the 
implantation cavity. 
