;;i S STUDIES ON PATHOLOGIC OVA. 



the fact, confirmed also by Fossati (1906), that a network can be revealed in 

 the stroma by the use of the Apathy, Golgi, Van Gieson, Mallory, and Cajal 

 methods of staining. This, however, does not necessarily demonstrate the 

 existence of a true reticulum. 



Rossi Doria (1905) found young villi which had not yet been invaded by 

 mesenchyme and emphasized that the two layers of chorionic epithelium had 

 not yet differentiated in Peters's ovum. Nevertheless, a reference to the illustra- 

 tion accompanying Peters's monograph shows very clearly the presence of short 

 villi containing stroma, even in this specimen. According to Rossi Doria, the 

 mesenchjane begins to appear first in the villi during the second week, at which 

 time they also begin to branch and become vascular. 



Friolet (1905), who examined a chorionic vesicle 11 by 12 by 9 mm., the age 

 of which he estimated as 3 to 4 weeks, concluded that villi arise by the extension 

 of the fetal mesoblast into the trabeculae of trophoblast, and regarded a. brush 

 border as a natural attribute of the syncytium. Friolet found the villi developed 

 better in the region of the basalis and especially around the whole periphery of 

 the mid-zone of the chorion. They were sparser in the capsularis, though without 

 degenerative changes. 



Kworostansky (1903) discussed the mesodermic structure of the villi, includ- 

 ing the Hofbauer cells, finding the stroma much as we know it now; but Michaelis 

 (1903) claimed to have found a granular line between the stroma of the villus and 

 the Langhans layer, which he regarded as indicating the existence of a definite 

 limiting membrane. Michaelis concluded that the existence of this membrane 

 finally disposed of the idea that the Langhans layer may arise from the stroma, but 

 anyone familiar with the appearances produced by Bielchowsky's stains between 

 the epithelium and the stroma of the villi will question Michaelis' conclusions. 



Von Lenhossek (1902) also recognized the existence of a basement membrane, 

 and Frassi (1906), upon the basis of material stained with silver nitrate, stated 

 that the villi in the greater number of moles have a limiting membrane, fibrous 

 in nature, which he regarded as "identical in form and structure with that demon- 

 strated and described in the villi of young placentae." However, Daels (1908 3 ), 

 from the use of Weigert preparations, concluded that a la}^er of fibrin, the product 

 of degenerative changes, forms between the exochorion and endochorion, and 

 Friolet, who at first could not find a membrana limitans, said to have been described 

 first by Langhans, found a definite hyaline zone in an abortus from the third 

 month. 



Happe (1906) found the villi of chorionic vesicles of the fourth to the sixth 

 week branched and about 2 to 7 mm. long, but nevertheless nonvascular. The 

 form of the youngest villi, which were about 2 mm. long, was said to be polyp- 

 like, the ends being swollen. Most of the villi of the three conceptuses from 

 the fourth to the sixth week showed an increase in caliber at the point of 

 branching, the swellings being especially marked at the origin of the terminal 

 branches of some of the villi. Happe stated that Hofbauer cells were not present 

 in the youngest villi, and that those of the older conceptuses contained only a few. 



