THE TROPHOBLAST AND ITS SURROUNDING BLOOD SPACES. 57 



sections, this band, although somewhat uneven, again appears. 

 Since here and there distinct cuboidal epithelial cells are visible, 

 one seems justified in pronouncing it surface epithelium, it then 

 would be a swollen rest which has remained between the two 

 coagulated blood droplets lying on the summit of the ovum. For 

 this reason there can be no association between the epithelial like 

 rows of syncytium and the surface epithelium. (Compare 

 Peters' Plate V Figs. 10 to 13, the epithelial like arrangement of 

 syncytial cells.) 



From this explanation one can understand how in Figs. 11 & 

 13 (Plate VII) syncytial cells arising from trophoblast (tr) 

 have become arranged in rows and finally terminate in a large 

 cluster of cells, (sy.) 



The same holds true as mentioned before for the syncytial pro- 

 cess (sy.) in Fig. 10 (Plate VI), which originates from the 

 trophoblast. 



In rather regular intervals but forming quite irregular arches 

 the trophoblast processes which at first have floated more or less 

 freely in the maternal blood spaces, approach the inner surface of 

 the ovular chamber (Fig. 6 tr. Plate III) and by means of 

 these arches subdivide the periphery of the chamber into smaller 

 blood lacunae. (Fig. 15 tr; Figs. 22 & 23 tr.) Thus these 

 lacunae develop within the trophoblastic shell of the ovum as is 

 so excellently shown in 'Plate I of Peters' work. 



Since the trophoblast excrescences and processes, as mentioned 

 above, are covered with a syncytium, it becomes obvious that 

 these blood lacunae are lined with a syncytial layer which is 

 plainly visible everywhere on the concave side of the arches. 

 (Fig. 23 sy.) In this manner the syncytium forms a line of 

 demarcation between the trophoblastic framework and the blood 

 lacunae. 



In comparing these blood lacunae in the periphery of the ovum 

 one notices at once a difference among them which one really 

 must expect and which also is noticeable in Plate I of Peters' 

 work. The lacunae lying near the summit are more or less 

 closed, while those situated in the depth and on both sides are, 

 by means of narrow channels, connected with the large blood 

 spaces in the decidua. This difference explains itself in the fol- 

 lowing manner: In the lacunae near the summit (Fig. 6 tr), the 

 closure of the arches is effected by the thin wall of reflexa or by 

 the fibrin cover, while this is impossible in the remaining portion 

 of the periphery. Here the vessel walls are opened as a result of 

 their rupture. (Fig. 6, c.) 



Whether the lacunae appear more closed or open, in both 



