286 STUDIES ON PATHOLOGIC OVA. 



That the placenta may continue to grow during retention after death of the 

 cyema was once firmly believed. This idea had its origin in the disproportion 

 frequently present between the size of the placenta and that of the cyema. At 

 present, belief in the growth of the placenta after death of the cyema seems to have 

 been abandoned, however. It was in connection with the placental changes, and 

 especially with changes in the vessels of the villi, that the question of the survival 

 and growth of cyemic tissues attracted attention. Among the placental changes 

 which suggested the presence of growth was the proliferation of the ectoderm of the 

 villi, indicated in so many specimens. It is interesting that Schickele (1907) re- 

 garded this apparent post-mortem proliferation as a direct cause of cyemic death. 

 Schickele believed that proliferation of the ectoderm of the villi results in encroach- 

 ment upon the placental circulation and ultimately in death of the cyema. It 

 seems strange, however, that Schickele (1905) stated that proliferation of the syn- 

 cytium usually does not occur, except in cases of long-standing retention. . Litt- 

 hauer (1887) also had believed in the continued growth of the placenta as a result 

 of retention, and had concluded that the death of the cyema was attributable to 

 interference with its nutritive supply through proliferation of the endometrium. 



Taussig (1903) stated that the vessels in the villi of retained "ova" may be 

 preserved for a long time, as reported also by Davidson, and Berlin believed that 

 obliteration of the villous vessels is a purely post-mortem phenomenon. As 

 previously stated, Berlin affirmed the belief of Merttens (1894) that the degree of 

 vascular obliteration somewhat parallels the duration of the retention. If this 

 obliteration actually occurs post-mortem, this conclusion of Merttens may be 

 correct, for it is well known that the degree of obliteration of the umbilical vessels 

 is dependent upon the duration since birth. However, the occurrence of ante- 

 mortem vascular changes established by numerous investigators can not be ex- 

 cluded. Nor is it necessarily an easy matter to differentiate the ante-mortem 

 from the post-mortem proliferative vascular changes. If the villi can continue 

 to grow after death of the fetus the rate of obliteration will be very much affected, 

 no doubt, by this fact. It is interesting that Graefe, although granting the possi- 

 bility of independent growth of the villi in retained uterine conceptuses, stated 

 that he saw hypertrophy of the villi only once. Schaeffer also believed that the 

 villi are preserved for a long time after death of the cyema, and Mall (1915) stated 

 that in cases of tubal pregnancy the villi may continue to grow independently 

 after death of the embryo. 



Crosti (1896) stated that if the ovum is not aborted immediately after death 

 of the embryo the villous capillaries gradually disappear. Crosti also believed 

 that the villi are preserved longer than the rest of the conceptus, and that even the 

 "appendici durate" may become hydropic. It must be borne in mind, however, 

 that the disappearance of the villous capillaries in consequence of maceration is 

 one thing, and the obliteration of the vascular lumen by proliferative processes 

 is quite another. Obliteration such as that represented in figure 177 illustrates 

 the former process, which is a purely post-mortem phenomenon as far as the partic- 

 ular villus is concerned, while that represented by No. 317, shown in figure 178, 



