456 VERA DANCHAKOFF 



nature, causes groups of mesenchymal cells to flow together 

 around tumor cells, and separate them from their original connec- 

 tions, encircling them entirely (figs. 5, 7, 9, 11, 12, 13, 14, 

 and 15). 



This encircling of the tumor cells is effected gradually and is 

 easily followed microscopically. A rounding up of the tumor 

 cell due to the contraction of its cytoplasm is brought about as 

 soon as mesenchymal splenic cells closely approach it. Tumor 

 cells with long processes at one side may be seen in preparations, 

 while at the other side they are rounded up and in close apposi- 

 tion to a strand of mesenchymal plasmodium. There is, there- 

 fore, a marked effect from the approach of the adult splenic 

 mesenchymal cell on the tumor cell, the latter withdrawing its 

 cytoplasmic processes and partly rounding up. At this tirqe it 

 may still be possible for a tumor cell to escape from the zone of 

 the closing mesenchymal ring, since there is yet no indication of 

 a structural change. The steadily and rapidly increasing num- 

 ber of tumor cells entirely encapsulated and cut off from the sur- 

 rounding tissue, speaks for the inertness of the tumor cell when 

 approached by adult splenic mesenchyme. Of the two, it is 

 the adult splenic mesenchyme which proves to be the more active 

 element, and as a result of this activity the tumor cell is com- 

 pletely immobilized and surrounded by a kind of plasmodial 

 capsule. 



Tumor cells only slightly changed or apparently not changed 

 at all, although in vacuoles, are invariably found nearest to the 

 healthy tumor tissue. The fact that the first structural changes 

 which can be detected appear only in tumor cells already en- 

 capsulated and that no apparently damaged tumor cells are found 

 outside of the vacuoles within the digestive zone can only be inter- 

 preted as evidence for the direct injurious effect of the mesen- 

 chymal cytoplasm on a living tumor cell. From the time the 

 tumor cell is situated within the intracytoplasmic vacuole of the 

 mesenchymal plasmodium, its fate is determined. It no longer 

 shows signs of that synthetic metabolism which enables a living 

 cell to maintain itself; it rapidly loses its characteristic cellular 

 structure, gradually disintegrates, and finally disappears entirely. 



