No. I.] GIANT CELLS OF THE MARROW. 121 



at Other times it is coiled upon itself, or appears simply as a 

 large, central mass, with projections from its surface; but in 

 most cases it shows incomplete constrictions of or partitions 

 from the peripheral membrane or layer of chromatin, which 

 tend to separate it into small nuclei comparable to those of the 

 typical marrow cells. The nucleus is granular, and in well-pre- 

 served specimens shows a distinct chromatin reticulum, with 

 conspicuous nodal points. In addition, one or many nucleolar 

 masses may be present, sometimes one apparently for each 

 incomplete small nucleus into which the large mass is divided, 

 sometimes only one for the entire nucleus, or in some cases 

 none at all. What I have called nucleolar masses or nucleoli 

 are distinguished from the large granules or nodal points of the 

 chromatin reticulum by their staining. In the triple stain of 

 hnsmatoxylin, eosin, and saffranin, the chromatin reticulum 

 takes the hjematoxylin stain as in nuclei generally, while the 

 nucleoli, like the nucleoli of the marrow cells, show a prefer- 

 ence for the saffranin, staining bright red when the time of 

 exposure to the different stains is properly adjusted. In a 

 number of instances, in the sections of the normal marrow of 

 adult cats, megakaryocytes were met with in which the nuclei 

 showed no chromatin reticulum at all, but stained diffusely 

 or almost so with the different dyes employed, taking the 

 stain like the nuclei of the matured form of nucleated red 

 corpuscle described in my paper upon the development of the 

 red corpuscles. In such cells where the chromatin was dif- 

 fusely scattered throughout the nucleus it frequently happened 

 that the nucleus was fragmented (Fig. i, c, f). It seems to me 

 that this appearance of the nucleus here as in the nucleated 

 red corpuscles is a sign of old age and death, and that these 

 cells are in process of dissolution, hence the fragmentation of 

 the nucleus. Arnold takes the directly opposite view, and con- 

 siders this appearance as one of the initial changes leading to a 

 fragmentation of the nucleus and division of the cell into 

 smaller marrow cells. 



According to Arnold, the following successive changes in 

 the structure of the giant cell occur, leading up to its fragmen- 

 tation. I. The first stage is characterized by an increase in 

 the chromatin substance, the chromatin filaments become more 

 numerous, form networks, etc., and toward the end of the stage 



