442 VERA DANCHAKOFF 



It is interesting to observe how resistant the tumor cells show 

 themselves even under unfavorable conditions. Occasionally in 

 a graft the ectodermal epithelial layer of the serosa does not give 

 way, and separates the grafted tissue from the mesodermic part 

 of the serosa and allantois. In the case of a graft of any other 

 tissue, it becomes quickly necrotic; but in the tumor grafts, 

 numerous cells survive for at least four to five days. At a 

 time when the mammalian mesenchyme and the endothelium of 

 the vessels grafted as a part of the tumor are dead (fig. 2) the 

 tumor cells still manifest an intense activity; they are frequently 

 found in mitosis and are seen to ingest dead tumor material 

 and mammaUan erythrocytes. It seems, therefore, that the 

 mammalian tumor cells are more readily adapted to rather 

 unfavorable conditions than are other cells of the mammalian 

 soma. 



The outer necrotic zone of the graft is gradually reduced by 

 the digestive activity of the tumor cells, and on the fourth or 

 fifth day of growth hardly any of it remains. The process of 

 growth in the first four to five days is very rapid and mitotic 

 figures are observed in great numbers. An illustration of the 

 growth of a tumor in the allantois on the third day is found in 

 figure 1. The group of tumor cells in the upper right corner is 

 adjacent to the central part of the tumor, of which the texture 

 is dense and in which the reciprocal relations of the cells are 

 not easily determined. In the peripheral zone of the tumor, the 

 cells, as represented in figure 1, are arranged in a loose manner 

 and almost all of them are connected by cytoplasmic processes, 

 and appear in the form of syncytia. In the extreme outer 

 zone of the tumor, the cellular syncytium is broken and small 

 groups of tumor cells are found dispersed within the mesodermic 

 layer of the allantois. Here the tumor cells are characterized 

 by long and slender processes which protrude into the loose 

 tissue of the allantois. Many cells are in mitosis, as the figure 

 shows. It is interesting to note the rounding up of the tumor 

 cells during mitosis in connection with the recent findings of 

 Robert Chambers, ^ who has shown that at this stage of the life- 

 history the cytoplasm of the cell becomes liquefied and the cell 



