338 ARTHUR WILLIAM MEYER 
It is of particular interest in this connection that Virchow 
(63) stated that Schroeder van der Kolk (’51) had concluded 
that large clear cells in the stroma of the villi, later classed among 
the physaliphores by Virchow, occurred too frequently to be 
correlated with hydatiform degeneration. This suggests that 
the so-called Hofbauer cells were known since the early days 
of cytology, and that some one must have noticed, even at that 
early date, that they were very common in some hydatiform 
moles. Whether or not this was van der Kolk I am unable to 
say, but that Hofbauer cells are especially numerous in some 
cases of hydatiform degeneration is undoubted. But it does 
not therefore follow that they constantly are present in this 
condition. Large numbers of Hofbauer cells occurred in seven- 
teen out of the sixty-one cases of normal and pathologic chor- 
ionic vesicles in which they were especially studied. Of these 
seventeen cases fourteen later were independently identified 
as showing hydatiform degeneration, and the other three were 
considered as possibly such. In other words, every case of this 
ser.es of so-called normal and pathological chorions in which 
the Hofbauer cells were numerous, was one showing hydati- 
form degeneration of the villi. It also is true, however, that 
thirty-four cases containing a few or some Hofbauer cells were 
not identified as being hydatiform moles, although three cases 
containing smaller numbers of these cells were so recognized. 
Moreover, not a single case of this series of sixty-one specimens 
which contained no Hofbauer cells whatever was later identi- 
fied as showing hydatiform degeneration. 
Somewhat similar evidence was afforded by the study of the 
twenty-two cases in the protocols of which Mall had noted that 
Hofbauer cells were present. Of these twenty-two cases, thir- 
teen later were identified as showing this degeneration. How- 
ever, since a total of 112 cases of hydatiform degeneration were 
identified among the 313 classed as pathologic among the first 
thousand accessions in the Mall collection, it is evident that the 
presence of Hofbauer cells was especially noted in but a rela- 
tively small percentage of the series of embryos classed as path- 
ologic. If we include certain other cases in which they came 
