CLARK: CYTOLOGY OF CARCINOMA. 227 



are eight indirect divisions, two direct. In the next there are 

 five indirect divisions, three direct. In a later (fig. 16), there 

 are five indirect divisions, four direct. In another (fig. 19), 

 there are four indirect divisions, three direct. This shows 

 consistently in this case that as the center of the nest is ap- 

 proached in the sections the number of direct divisions increase 

 in proportion while the indirect decrease in proportion. In the 

 region of the arrow point of figure 16 an enlarged drawing was 

 made (figure 17). I used this to show more detail about the 

 cells shown in figure 16. Cell A was on the edge of the necrotic 

 area. Its chromatin was small in amount and gathered in two 

 clumps in one segment and three in the other. Cell C is an 

 ordinary dividing cell. Cell D is in the second row from the 

 necrotic edge. The cross-hatched work shows the necrotic 

 area, this area being entirely necrotic and showing no transi- 

 tion cells along the edge. 



Figure 18. There are but two dividing cells in the upper 

 segment of this nest, while in an earlier there are fourteen, the 

 number decreasing with each section until this one. They 

 have increased steadily in the middle part of the limb, however, 

 from eleven to nearly twenty in the section shown in figure 18. 

 This carefully worked out will demonstrate that at the same 

 time the cells in one part of the nest are rapidly dividing those 

 in another part are not dividing at all. There is either an 

 unequal stimulus to growth in the nest or an unequal negative 

 cause. 



Figure 19. This nest is the same one as that in the preced- 

 ing figure, but in this section the two parts have been sepa- 

 rated. At the point of the arrow is the location of figure 20, 

 and here are shown the three dividing cells drawn in figure 20. 

 In figure 20, cell A is plainly among the degenerating cells in 

 the necrotic plug, and is surrounded by "chromatic cells," no 

 vigorous cell being near. It is a large clear cell with a biseg- 

 mented nucleus and showing but very little chromatin. Its 

 appearance indicates that it is a degenerating cell. Cell B 

 lies just outside the border of vigorous cells. Its nucleus is bi- 

 segmented and it stains much deeper than the cytoplasm. The 

 chromatin nucleoli stain very faintly. Cell C is a large clear 

 cell lying in the third row of cells from the necrotic edge. It 

 stains lighter than the other cells about it and shows a small 

 amount of chromatin and that stained faintly. Cells A and B 



