392 Maximilian Herzog. 



laries and veins can also be seen at a distance from the border 

 zone in the spongiosa and compacta of the decidua extending nearly 

 to the surface. In the border zone of our specimen near the 

 inner pole of the ovum there is a large irregular blood sinus about 

 1 to 1.5 mm. in diameter, which has been completely opened by 

 the trophoblast and is in free communication with the blood-filled 

 cavities of the trophoblast. On its inner side (towards the mus- 

 cularis) this sinus is still lined by vascular endothelium. The wall 

 towards the trophoblast has been extensively destroyed, so that the 

 large blood space is lined on one side by much stretched but still 

 fairly well preserved endothelium, and on the other by the irregular, 

 ragged trophoblast. The border zone at the base of the ovum 

 also shows many large cystic gland spaces filled with blood. Most 

 of them can be recognized as derived from glands by remnants of 

 dropped-off, degenerating epithelium, while the densely filled blood 

 spaces, on the other hand, can be identified by their endothelial lining 

 and the remnants or dropped-off floating portions of the same. But 

 there are some cystic blood-filled spaces which cannot be readily 

 identified as being originally glands or blood vessels. Nowhere in 

 the border zone does the glandular epithelium or vascular endothe- 

 lium show any proliferative processes ; degenerative processes only 

 are seen. 



At the base of the ovum in the layer of the border zone nearest 

 to the trophoblast a small, rather delicate strip of canalized fibrin 

 is found. This strip consists of a network of fibrin in which are em- 

 bedded decidual cells, red blood corpuscles and poly nuclear leucocytes. 

 There is a more powerful mass of fibrin found in the equatorial 

 tract of the border zone. This mass (Fig. 28) contains rather coarse 

 threads of fibrin and great numbers of red blood corpuscles. It 

 appears that this mass has formed in and is filling out the lumen 

 of an enlarged blood space. 



We have described how the trophoblast in approaching the cap- 

 sularis sends out bands and filaments of cells which become fused 

 with and are lost in the thin capsular strip. The same process 

 can be seen around the whole periphery of the trophoblast. Par- 

 ticularly around the equatorial plane the syncytium can be seen to 



