GIANT-CELLS OF BONE-MARROW 307 
ess. There can be no question here of mitotic proliferation, 
since at least the apical half of the enamel organ, from which 
the cells are taken, is atrophic and clearly in process of degenera- 
tive transformation into the so-called Nasmyth’s membrane of 
the soon-to-be erupted tooth. These multinucleated giant-cells 
are of ectodermal origin; they are formed by the fusion of cells 
of the enamel pulp into large irregular syncytia. These syn- 
eytia are comparable to the osteolytic giant-cells (osteoclasts) of 
the marrow of developing bones, and in general to foreign-body 
eiant-cells of pathologic foci. They contain globules of resorbed 
enamel. The definitive enamel of the preerupted tooth is 
apparently reshaped to some extent prior to eruption, and the 
superfluous decalcified enamel is ingested by these amelolytie 
viant-cells. These cells supply seemingly unequivocal evidence 
regarding the origin and significance of the chromatic rodlets 
and masses which superficially suggest so strongly the chromo- 
some configurations of multipolar mitoses. ; 
In cell figure 25 the relatively small spheroidal nuclei have 
assumed a diffusely chromatic appearance, with only relatively 
very few karyosomes, and the nuclear reticulum is barely dis- 
cernible. The chromatin material has diffused throughout the 
nuclei and given to them a cloudy, more deeply staining, appear- 
ance. At a later stage (fig. 26) the chromatin has become aggre- 
gated into one or several larger or smaller peripheral, frequently 
crescentic, masses. Occasionally one or several larger or smaller, 
irregularly spheroidal or bacillary, chromatic masses occur 
within the now very pale, and only vaguely outlined, nuclei. 
This condition is clearly indicative of degeneration. Already at - 
these stages certain of the chromatin aggregations have passed 
into the cytoplasm, with the disappearance of the nuclear mem- 
branes. These chromatin masses thus formed are clearly not 
eenuine chromosomes in the usual sense, and of normal consti- 
tution, though they closely simulate chromosomes, and may 
possibly have even an identical chemical nature. They are 
formed, like chromosomes, from the nuclear chromatin, but in 
an entirely different manner, and without the intervention or 
assistance of centrosomes or spindles, 
