328 STUDIES ON PATHOLOGIC OVA. 



they are firm, and are located halfway between the serotina and the tips of the 

 villi. In figures 3 to 5 accompanying his article, good representations of sec- 

 tions of villi with nodules partly embedded in the stroma of the villi are found. 

 Heinz believed that they became separated from the rest of the maternal tissues 

 by the growth of the villi, and thus became isolated and related to the latter. He 

 thought that as the villi develop they begin to devour the maternal tissue with 

 which the implanting conceptus is in contact, and that these nodules represented 

 the only remnants of these maternal tissues. While Langhans thought that these 

 nodules are formed merely by the invasion of the maternal by the fetal tissues, 

 Heinz believed that they resulted from an invasion of the maternal tissues 

 by villi, with accompanying destruction of the former. In support of his opinion, 

 he referred to the well-known destructive power of the villi first revealed by 

 Virchow, who called attention to the invasion of the maternal blood-vessels by 

 fetal villi. 



Minot (1889), contrary to Heinz, declared that the nodules within the villi are 

 commoner in old placentae, a conclusion which prompts the inference that Minot 

 may have regarded them and the so-called decidual islands of contemporary litera- 

 ture as identical. 



Hofmaier (1890), in describing his Case V,a conceptus 20 by 5 mm., containing 

 an embryo of 4 mm., stated that small nodules the size of the head of a pin were 

 present everywhere on the villi. These nodules the author regarded as composed 

 of decidual cells. 



Kossman (1892) also spoke of insular nodules of maternal tissue and made 

 fine drawings of sections cut 3 to 4 /z thick. He declared that it was plain that 

 these nodules were composed of decidual tissue in which some of the villi be- 

 came embedded, his idea being that portions of decidua became isolated from 

 the rest and then were retracted by villi which lost their attachment to the 

 decidua. Kossman stated that he never found nodules covered entirely by 

 syncytium, as reported by Kastschenko, and doubted the occurrence of such. 

 He further concluded that the cells composing these nodules do not simulate 

 those composing the Langhans layer nearly as closely as Kastschenko had stated. 



Crosti (1896) also spoke of these nodules and referred to them as appendici 

 duraie, saying that they become hydropic in retained conceptuses. 



In discussing conceptuses of the sixth week, Webster (1901) stated that he 

 could distinguish three kinds of "Zellknoten." One was said to be composed of 

 "undoubted decidual cells, along with a mass of cells which evidently belong to the 

 proliferated Zellschicht at the end of an attached villus." These were said to be 

 surrounded more or less by syncytium and might contain portions of it and also of 

 the villi. Webster regarded this form of nodule as due to decidual elevations upon 

 which the villi were implanted. A second form of Zellknoten was said to be com- 

 posed solely of closely placed villi, along with several processes or strands of the 

 syncytial layer. The third variety was said to be composed of villi surrounded by 

 fibrin. 



