CHAPTER XVI. 



VILLOUS NODULES. 



That the occurrence of numerous small nodules on the villi of young concep- 

 tuses must have attracted the attention and aroused the curiosity of early embry- 

 ologists, one can not doubt. They often are so conspicuous, so spherical, and, when 

 located on the tips of the villi, also so striking in appearance, that they could not 

 be easily overlooked. Hence it does not surprise one that Miiller (1847), in his 

 interesting monograph on moles, described them, and that Sommering (1799) had 

 represented them, as figure 284, reproduced from the latter, shows. Miiller re- 

 marked that he did not always find them, and that they sometimes were absent 

 in normal specimens. As will appear later, this is a very interesting and probably 

 also a significant observation. Langhans (1877), in connection with a thorough- 

 going microscopic examination of the placenta, spoke of these appendages as 

 "insular nodules of maternal tissue," and also represented one. Langhans spoke 

 of them as being 1 mm. in diameter, and said that their white color and turbid 

 nature distinguished them from the more transparent swellings of the villi them- 

 selves. Their form was said to vary, and some were found to be located on the 

 curved, enlarged processes of the villi, while others capped these processes. Micro- 

 scopically, they were said to be composed of large, oval, round, polyhedral, spindle- 

 and star-shaped cells, usually a little flattened, which could easily be distinguished 

 from the fetal cells by their size alone. Langhans stated that the cells composing 

 these islands were decidual in origin, but that their nuclei were the size of the 

 nuclei of the epithelium which separated them from the stroma of the villus. 

 Langhans regarded them as decidual prolongations which penetrated the fetal 

 placenta, and which hence might appear on the surface of the chorionic membrane 

 itself. 



As long as the exact origin of the placenta had not been decided at this time, it 

 need not surprise one that Langhans should speak of these nodules as being composed 

 of maternal tissue. Moreover, everyone who has examined conceptuses still 

 implanted in or aborted with the decidua will admit that often it is impossible to 

 draw a definite line of separation between the cells composing these nodules and 

 the adjacent decidua. But it is not unlikely that exact differentiation between 

 the two tissues is possible by the use of histochemical methods. 



Kastschenko (1885) referred to the insular nodules of Langhans merely as 

 cell nodules (Zellknoten), and stated that they are always composed of chorionic 

 epithelium. It is not clear to me, however, whether Kastschenko did not, after 

 all, confuse these nodules with syncytial buds. Besides, he stated that, although 

 these cell nodules develop from the epithelium of the chorion, they later become 

 serotina cells. 



Heinz (1888) stated that the "insulae of maternal tissue" are especially common 

 in placenta from the third to the sixth month, and that he never found them at 

 term. He concluded that they are always composed of maternal tissue, that 



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