PLASMA CELLS OF HOFBAUER 335 
and the interstitial cells, both of which he conceived as exercis- 
ing a protective réle. Muggia (’15), too, instead of regarding 
the lipoid interstitial cells of Acconci as degenerate, emphasized 
his belief that they are particularly resistant to degeneration, 
being found perfectly preserved in the midst of detritus. Since 
the young connective-tissue cell loses, or rather retracts, its 
processes as it becomes converted into a Hofbauer cell, it need 
not surprise us that the latter survives the former. Retraction 
of the processes contributes to the apparent increase of cyto- 
plasm of the rounded swollen cell and also is involved in the 
formation of the spaces in which these cells usually lie. Mug- 
gia, who considered the cells found by him in great numbers in 
a case of partial hydatiform degeneration, as identical with 
those described by Acconci, gave a fine detailed description 
absolutely typical of the cells described in greatest detail by 
Hofbauer. Moreover, the excellent illustrations which accom- 
pany Muggia’s article leave no doubt as to the identity of the 
cells or of their degenerate character. Muggia stated that these 
cells in normal villi increase until the end of the fifth month, 
when, according to Savare, they are most numerous. Muggia 
further found numerous cells very similar to the interstitial 
cells of Acconci, or “the plasma-like cells of Hofbauer,’ which 
he says are regarded by some as early stages of interstitial cells 
and by others as mast cells, although he regarded them as par- 
tially differentiated interstitial cells. 
Until I had seen sections of the chorion of embryo no. 1531, 
I was largely at a loss to know why Hofbauer cells so frequently 
were described as lying in gaps or spaces in the mesenchyme. 
However, in this specimen cross-sections of a number of villi 
showed splendid examples of this condition, which alone made 
the cells very conspicuous. The cells often were very numer- 
ous, in fact more numerous than the mesenchyme cells which 
remained, although some well-preserved villi contained no Hof- 
bauer cells whatever. Some of the younger specimens also 
contained none. This was true of a chorionic vesicle with an 
embryo 1 mm. in length. They were found most commonly 
in the villi, but not infrequently some of them lay in areas of 
