PLASMA CELLS OF HOFBAUER 343 
bauer found that in fresh material these cells reacted as plasma 
cells to vital stains. 
The opinion of Minot that Hofbauer cells are degenerating 
erythroblasts probably can be accounted for by the fact that in the 
chorionic vesicle from which Minot’s series, showing a progres- 
sive degeneration of the latter into the former, was obtained, 
it was impossible to distinguish between the two. This diffi- 
culty was due partly to the poor state of preservation of the 
particular specimen, a larger survey, especially of better mate- 
rial, would have revealed the fact that Hofbauer cells are found 
in villi, the blood-vessels of which contain no erythroblasts. 
Moreover, as will appear later, the distribution of these cells in 
the villi is not such as one rightfully would expect if they have 
their source in the vessels. However, since the final form of 
the typical Hofbauer cell is a mere shadow cell, it necessarily 
may be impossible to determine the kind of cell from which this 
shadow form arose, for, as is well known, the end forms in 
processess of degeneration of many different types of cells are 
indistinguishable. Consequently, a group of swollen, highly 
vacuolated cells also may contain among them degenerated, 
nucleated red blood cells, as Minot held. Indeed, degenerat- 
ing erythroblasts which are indistinguishable from some Hof- 
bauer cells, can be seen occasionally not only in the vessels, 
but in the heart and also within the cavity of the chorionic ves- 
icle; but such occurrences do not prove that the Hofbauer 
cells of the villi arise from erythroblasts. That this usually 
is not the case follows also from the fact that well-preserved, non- 
vacuolated Hofbauer cells occur in villi which have not become 
vascularized or which, as stated above, no longer contain ves- 
sels. It is true that it often is impossible to distinguish be- 
tween degenerate erythroblasts within the vessels and Hof- 
bauer cells lying outside of, even if near to them, in the stroma 
of the villus. This difficulty is entirely avoided by examin- 
ing the older specimens without nucleated reds, for, since Hof- 
bauer cells always are nucleated except in their very last stages, 
confusion with nucleated cells thus is avoided. 
THE JOURNAL OF MORPHOLOGY, VOL. 32, NO. 2 
