404 GYNECOLOGY 



bans' layer. Wherever the chorion comes into contact with the 

 maternal decidua, evidence of invasion of the latter by the former 

 is found, but it is chiefly noticeable at the site of the placental por- 

 tion of the chorion, the decidua serotina. Here in the early weeks 

 of gestation irregular extensions of syncytium may be found. They 

 are chiefly noticed in the compact layer of the serotina, but are 

 observed in the spongy layer, and even in the muscular wall. Por- 

 tions undoubtedly extend into maternal blood sinuses, to whose 

 walls they may become attached. Small portions of syncytium 

 also may be carried away in the venous circulation. That this may 

 take place throughout a considerable period of pregnancy is highly 

 probable. Several authors hold that pieces of villi, comprising 

 both epithelial and connective-tissue elements, may also be de- 

 ported, though I have never observed this in normal specimens. 

 Whatever be the extent of the process no important anatomic les- 

 io'ns in the vessels of the lungs or elsewhere have been demonstrated 

 to result from them. The chorionic fragments are very small and 

 are probably rapidly disintegrated in the maternal blood. Their 

 destruction is explained according to Ehrlich's now well-known 

 hypothesis. The foreign fragments produce a substance which 

 fixes them to the red blood cells, and which also enters the serum, 

 forming an antitoxin, which tends to destroy the fragments. Veit 

 has termed the latter syncytiolysin. Various experiments have 

 been made in support of the view that the chorion produces a toxin 

 which may cause various morbid changes during pregnancy un- 

 less continually destroyed by the maternal organism. Thus Politi 

 injected sterile filtered extract of human placenta into rabbits, 

 producing death in some cases with spasms and marked prostra- 

 tion. He states that the toxicity of the extract was lowest when 

 the placentas of healthy women were used and most marked in 

 the case of eclamptics. Ascoli has also made interesting experi- 

 ments, in which placental infections produced some of the pheno- 

 mena of eclampsia. Beside the influence of the blood in counter- 

 acting the syncytiotoxin, it is believed by some that the decidual 

 cells also share in this function. Bandler holds, in addition, that 

 the ovary also furnishes an element in its secretion which is anta- 

 gonistic. 



Functions of the Placenta. It has been clearly established that 

 the placenta is entirely an organ of the chorion, consisting of pro- 

 jections of the latter termed villi, which are attached to the uterine 

 mucosa, and bathed by maternal blood circulating among them. 



Comparatively little is known as to the nature of the inter- 

 change of materials between the fetal and maternal circulations 

 through the medium of the villi. For many years the placenta has 

 been regarded merely as the medium through which nutritive 



