290 H. E. JORDAN 
regressive and disintegrative changes in the atrophying yolk-sac 
and the morbid marrow, respectively. The experimental evi- 
dence suggests that the intracellular erythrocytogenic activity 
of the ‘hemogenic giant cells’ is of negligible physiologic signifi- 
cance. 
The various microscopic preparations of the red bone marrow 
of the rabbit and the guinea-pig offered a favorable material 
for the study of the enigmatic and disputed significance of the 
so-called mitotic figures, variously atypical and apparently 
multipolar, of the giant-cells, and of the data suggesting an 
intracellular erythrocytogenic function of these cells. It will 
conduce to a simplification of the analysis of the complete prob- 
lem to consider the latter matter first. 
II. CYTOLOGIC 
INTRACELLULAR ERYTHROCYTOGENESIS 
Review of literature 
This phase of the subject involves the question of the origin 
of the multiple nuclei of the polykaryocytes and the significance 
of the occurrence of granulocytes and erythrocytes in the giant- 
cell cytoplasm. Arnold (1, 2) describes a mode of nuclear 
division in the rabbit’s marrow which he terms ‘indirect frag- 
mentation.’ This he claims is followed by a division of the 
cytoplasm, which produces separate mononucleated and poly- 
morphonucleated leucocytes. According to Arnold, therefore, 
these cells divide by a method, essentially amitotic, an inter- 
mediate phase of which process is represented by a multinu- 
cleated giant-cell. Heidenhain (8) recognizes amitotic nuclear 
multiplication, but regards multipolar mitosis, unaccompanied by - 
cytoplasmic division, as the more importantand the preponder- 
ant mode of nuclear proliferation. He interprets the presence 
of granulocytes as the result of an invasion, not phagocytosis. 
Pugliese (15) interprets the presence of erythrocytes and leuco- 
cytes in the giant-cell cytoplasm as the expression of an endoge- 
nous hemocytogenic capacity. Foa (7) also describes an intra- 
