GIANT-CELLS OF BONE-MARROW 299 
constitute themselves into nuclei, while the cytoplasm divides. 
This process he considers comparable to the multiple mitoses of 
pathologic tissues. The cytoplasm of these ‘dividing’ cells fre- 
quently contains an enormous vacuole. Denys was unable to 
detect either centrosomes or archoplasmic spindles in these so- 
called dividing cells. It may be said at once that Denys’ illus- 
trations do not support his description of the alleged chromosomes | 
as U-shaped nor do his figures show any evidence of a longi- 
tudinal splitting of the chromatic rods nor does he give any fig- 
ures showing a transition between the stage illustrated in figure 
5 (‘anaphase’) and the alleged later one when the nuclei have 
been reconstituted (figs. 16 and 17); nor does he illustrate the 
alleged later cytoplasmic division in the rabbit’s marrow. An- 
other significant fact to which allusion will be made later con- 
cerns the uniformly much smaller size of the cells which are said 
to be in mitosis. This is well illustrated in our figures 5, 6, 12, 
14, and 15. 
In the alleged mode of division described by Arnold (2) as 
‘indirect fragmentation’ four main steps are recognized. In the 
first stage the nucleus becomes diffusely chromatic (fig. 8); in 
the second it stains more intensely and the interlobular constric- 
tions enter more deeply into the nuclear substance, and the form 
of the nucleus as a whole becomes more complex (fig. 20); this 
stage is followed by one where the chromatin becomes segregated 
into unequal masses, constituting new young nuclei; and in the 
fourth or final stage the cytoplasm divides into portions equal in 
number to that of the daughter-nuclei. The process above out- 
lined seems clearly to signify only regressive degenerative 
changes in polymorphokaryocytes. The alleged intracellularly 
derived leucocytes of his figure 10 should be interpreted as 
invading cells. 
Heidenhain (9) describes a process of incomplete division of 
these cells by mitosis, in which process the centrosomes (200 to 
300) are said to take an important part. Multipolar mitotic 
figures are said to form without leading to a final division either 
of nucleus or cytoplasm, but effecting a refusion of groups of 
chromosomes into a new polymorphous nucleus. No details 
