GIANT-CELLS OF BONE-MARROW 295 
correct to interpret its occurrence under certain conditions as 
atypical or as a chance variation. 
But Dickson’s conclusion that the presence of erythrocytes 
(and leucocytes) in hemogenic giant-cells signifies a phagocytic 
activity on the part of the giant-cells cannot be substantiated. 
In the first place, the vast majority of the hemogenic giant-cells, 
whether in yolk-sac, normal marrow, or pathologic marrow, con- 
tain no cell inclusions. It is only very rarely that an erythro- 
plastid is included. Erythroblasts are more common. If these 
cells were phagocytosed it would seem that the relatively more 
senile cells should preponderate, rather than the younger types. 
Nor does it seem likely that these erythroblasts invaded the 
giant-cell cytoplasm. They undoubtedly possses some ameboid 
capacity, but if they had any predilection for the sites of giant- 
cell cytoplasm, they would be expected to be more abundantly 
found. 
There is, however, one other contingency that must be reck- 
oned with, not heretofore suggested to my knowledge. It must 
be remembered that the cellular elements of active red bone- 
marrow are very closely packed; also, cells of certain types occupy 
distinct areas where they proliferate extensively. In other words, 
one does not find all types of cells scattered promiscuously 
throughout the entire red marrow, but one finds nests of erythro- 
blasts distinct from nests of eosinophilic granulocytes. It ap- 
pears as if an erythrocyte progenitor proliferates greatly in one 
area, and a granulocyte progenitor in another area. If such a 
locus of erythroblast proliferation abutted on a giant-cell, as 
frequently happens, it is conceivable that one or several of the 
more peripheral cells could become forced into the less resistant 
peripheral cytoplasm of the giant-cell. But when all these con- 
tingencies are fully recognized and given due weight with regard 
to a certain number of included erythrocytes, there persists a 
considerable residuum of consistent cytologic evidence in yolk- 
sac, normal marrow, and pathologic marrow to warrant the 
ascription of at least a slight erythrocytogenic function to these 
enlarged hemoblasts, the several varieties of hemogenic giant- 
cells. 
