CLARK: CYTOLOGY OF CARCINOMA. 2l3 



In the cells shown I have drawn them as they appeared in out- 

 line in one plane, but included the chromatin through the depth 

 of the cell. Each well-defined segment of the nucleus usually 

 contains a chromatin nucleolus. In cell A the lower nuclear seg- 

 ment has a second cleft appearing upon its inner border. Cell 

 B has two distinct nuclear segments, each one of which has a 

 secondary groove appearing upon its upper surface. The 

 upper segment shows no chromatin at all. Cell C shows two 

 nuclear segments, each containing a chromatin nucleolus. Cell 

 D shows a central constriction of its nucleus with the mother 

 chromatic mass in the plane of constriction, but I do not say it 

 is in the process of division. 



Cell £■ is a representation of the typical indirect division 

 figures found in this material. It is in the early anaphase. 

 As I have already said, this material, being fixed in formalin 

 with no particular care regarding its cytological preservation, 

 shows no detail characteristics of the chromosomes. I have 

 used in my counts only the well-marked division figures, from 

 the close spireme stage on. In these indirect divisions the 

 cells are larger than the resting cells, the nuclear membrane 

 had disappeared, and about the chromatic figure the cytoplasm 

 was clear. I was unable to make out the spindle or any of the 

 details farther than shown. 



Cells F F are two fragments of degenerated cells in each of 

 which the chromatin has swollen and coalesced into one homo- 

 geneous, deeply staining mass. 



Figure 2. Among the cells of this group there is not the 

 noticeable difference in size usually seen between the dividing 

 cells and the resting ones. Cell A shows an indirect division 

 plainly. Cell B shows the nucleus being divided by a cleft 

 passing in from its upper surface. Each segment contains a 

 chromatin nucleolus. Cell C, an otherwise ordinary resting 

 cell, contains in its cytoplasm, half way from the cell border 

 to the nuclear membrane, a clear vesicle, regular in outline 

 and with a definite limiting border indicating that it is filled 

 with a substance differing from the cytoplasm. 



Figure 3 shows no new structures, but attention is called to 

 the regularity of the chromatin nucleoli. Cells A and B show 

 the nuclei entirely segmented and each segment containing 

 regular chromatin nucleoli, the lower segment of cell B con- 

 taining two, 



