PROBLEMS IN OBSTETRICS AND GYNECOLOGY 403 



In normal cases of pregnancy it is considered that there is es- 

 tablished a kind of equilibrium between the ovum and maternal 

 organism; that in some abnormal cases the ovum suffers as the 

 result of predominant activity of the maternal elements, while in 

 others the maternal organism suffers when the ovum is in the as- 

 cendant. In the former instance the ovum may be destroyed and 

 abortion result; in the latter the mother may exhibit phenomena 

 of various kinds, from the minor nervous and alimentary disturb- 

 ances of pregnancy to such marked disorders as pernicious vomit- 

 ing or eclampsia. This same theory would also explain the rapid 

 growth of chorionic tissue after pregnancy, giving rise to chorio- 

 epithelioma malignum, as mainly due to some defect in the ma- 

 ternal factors which normally counteract the excessive proliferation 

 of chorionic epithelium. 



These newer lines of thought have followed close upon the es- 

 tablishment, by recent workers, of the exact histologic relation- 

 ships between the human ovum and uterus. It has been demon- 

 strated beyond doubt that the early ovum in its vesicular stage is 

 characterized by a proliferation of its outer epiblastic covering 

 forming a layer of cells, distinct from one another, known as the 

 trophoblast, and that through the activity of this layer the ovum 

 burrows into the superficial part of the uterine mucosa, where it 

 becomes completely imbedded. The trophoblast continues to ex- 

 tend outward in all directions, lacunas appearing in it. Into the 

 latter, blood finds its way from maternal sinuses which have been 

 opened by the phagocytic activity of the trophoblast. The entire 

 trophoblast is in this way converted into a sponge-like structure. 

 The lacunas enlarge, and the trabeculas between them become 

 smaller. The former are the forerunners of the permanent inter- 

 villous spaces of the placenta, the latter of the villi. The tropho- 

 blastic cellular trabeculas are gradually penetrated by the meso- 

 blastic layer of the chorion in which the terminal branches of the 

 umbilical vessels carry on the fetal circulation. As soon as lacunas 

 appear in the trophoblast a change takes place in the cells of the 

 latter lining the lacunas. They appear to become fused into a con- 

 tinuous layer of nucleated protoplasm in which no cell outlines 

 can be distinguished. This is the earliest stage in the formation 

 of syncytium, and was regarded by Peters, in whose specimen it 

 was demonstrated, as caused partly by the pressure of the maternal 

 blood in the lacunas, partly by the influence of the blood-plasma; 

 in some parts, also, blood-corpuscles appeared to become degen- 

 erated and to fuse with the trophoblastic cells. 



As pregnancy advances, the syncytium rapidly increases so that 

 it covers the entire chorion. The unaltered trophoblast cells sub- 

 jacent to the syncytium form the layer universally known as Lang- 



