HOFBAUER CELLS. 309 



may be in a state of hyperactivity or of degeneration, and questioned the state- 

 ments that Hofbauer cells appear only at the end of the fourth week and that they 

 have a short life. Pazzi regarded the Hofbauer cell as fundamentally a constit- 

 uent of the villi, as the decidual cell is of the decidua. He, like Essick, attributed 

 their origin to the endothelium of the vessels, and further suggested that the Hof- 

 bauer cell may have a special internal secretion intended to preserve the stroma 

 of the young villus against degeneration. Pazzi also considered the question 

 whether a Hofbauer cell can transform itself into an epithelial cell and finally into 

 a syncytial cell, and added that the invasion of the stroma of the villus by epithe- 

 lial growths, such as represented in figure 119 (plate 10, Chap. VIII), is only a 

 special development of Hofbauer cells! 



As already stated, Muggia also found these cells very abundant in a case of 

 partial hydatiform degeneration, and held that their appearance and condition are 

 correlated with proliferation and vacuolation of the syncytium, maintaining that, 

 as the latter becomes vacuolated, the lipoid interstitial cells of Acconci appear, 

 the changes in the two being wholly parallel. 



Since 32 of the 51 chorionic vesicles in this series of 61 containing a few, some, 

 or many Hofbauer cells had been classed among the pathologic, it follows that 

 these cells were noticed more frequently in the pathologic than in specimens 

 classed as normal. This becomes especially evident if we exclude from this series 

 of 51 cases all those containing some or many Hofbauer cells, for of 27 of these, 

 19, or 70.4 per cent, had been classed among the pathologic. Moreover, since the 

 great majority of the conceptuses classed as normal are abortuses, one would be 

 entirely justified in questioning the strictly histologically normal nature of the 

 chorionic vesicles which accompany some embryos classed as normal. At any rate, 

 it is evident that the plasma cell of Hofbauer is associated with degenerative 

 changes in the mesenchyme of the villi. Since such changes are more common in 

 abortuses classed as pathologic, it is not surprising that Hofbauer cells are more 

 common in the latter than in normal specimens, and, since degenerative changes in 

 the stroma are especially pronounced in advanced cases of hydatiform degeneration, 

 it is still less surprising that Hofbauer cells are particularly common in this con- 

 dition. But they are not necessarily pathognomonic of hydatiform degeneration, 

 although it is true that when at all numerous they are associated with hydatiform 

 degeneration in about 75 per cent of the cases. 



It also should be recalled that the great majority of the specimens classed as 

 pathologic microscopically show the presence of both degeneration and macera- 

 tion. However, it never was the most macerated but the most degenerate speci- 

 mens in which Hofbauer cells were most numerous. Hence, whatever the cause 

 of this transformation of the mesenchyme into Hofbauer cells, it may also be 

 the cause of hydatiform degeneration. 



After a careful survey of a considerable number of specimens, both normal 

 and pathologic, ectopic and uterine, of human abortuses of widely different ages, 

 I am led to concur entirely in the opinion of Minot that the typical vacuolated 

 cell, as described by Hofbauer, is a degeneration product, though usually not a 



