THE TROPHOBLAST AND ITS SURROUNDING BLOOD SPACES. 59 



almost throughout, is lined with an enclothelium. In the im- 

 mediate neighborhood of the blood lacunae, in the loose tissue, 

 numerous large syncytial cells are found singly or in clusters, 

 some of them lying close to the chamber wall. These cells, so to 

 say, are the pathfinders for the syncytimn, which glues the 

 trophoblastic processes to the wall. For this reason a great num- 

 ber of large syncytial cells are met with in the sections which 

 pass far laterally through the ovum. (Fig. 4 sy. Plate II.) 



It is noteworthy that wherever a syncytial cell lies close to 

 a vessel wall the corresponding endothelial cell on the inside, in 

 comparison to others, seems enlarged and contains a very large 

 nucleus which either is oblong or undergoing segmentation. 



One could feel inclined to think that the transformation of the 

 endothelium into syncytium is the primary result and that the 

 syncytium develops further from here. One then could con- 

 clude that the syncytium in the main originates from vessel en- 

 dothelium. In our specimen, however, no support whatever can 

 be detected for such an assumption. As a matter of fact, the 

 conditions are as follows : The syncytial cells which cover the 

 trophoblastic processes and attach themselves to the walls enter 

 the tissue, become disseminated between the capillaries and 

 glands especially in the remaining framework of tissue. They 

 attach themselves to the walls of the capillaries which are still 

 closed, corrode them and thus constantly open new blood 

 spaces. 1 



This process, e. g., is represented in the sections 86 to 89. Here 

 we see large rows of syncytial cells which advance from a 

 trophoblast process towards the wall of a transversely cut cap- 

 illary and attach themselves to cells of the wall. (Fig. 28 sy. 

 Plate XVI.) In the next section syncytial cells pass into a ves- 

 sel wall. Its various layers become detached from each other. 

 The tissue cells which formerly lay in closed arches as well as 

 the endothelial cells are now unraveled. In the next sections we 

 see blood cells oozing from these unraveled vessel walls. The 

 syncytial cells force their way deeper and deeper into the lumen. 

 Finally one sees only half of the wall of the vessel until this, too, 

 is dissolved. In this way the peripheral blood spaces, one after 

 the other, are destroyed by the never ceasing action of the syn- 

 cytial cells and from these findings the conclusion must be drawn 

 that already, /. c., even in this early stage of development, the 

 intervillous spaces are indicated and even existing. 



1 At the Congress in Kiel, Peters demonstrated drawings which show beautifully how 

 endothelial cells become detached and necrotic exactly at those places where syncytial 

 cells have attached themselves to the outside of capillaries; another proof that endothelial 

 cells do not transform into syncvtium. 



