208 VERA DANCHAKOFF. 



and rounding up, how the tumor cells gradually lose their 

 structure TV, their cytoplasm becoming vacuolized, their nuclei 

 pycnotic and how finally the tumor cells disappear entirely. 



Now in respect to the small lymphocytes, may they not be 

 still connected in some indirect way with the disappearance of 

 the tumor cells? Round-cell infiltration has been described 

 around the disappearing tumor grafts within the allantois. But 

 though the small lymphocyte is a round cell, not every round cell 

 is a small lymphocyte. Round cell infiltration exists indeed 

 around such grafts. This infiltration, however, at a closer study 

 proves to consist not of small lymphocytes, but of round, mobile 

 cells of hemoblastic nature which, as mentioned above, differ- 

 entiate into granular leucocytes. As has been shown in one of 

 my previous papers, the small lymphocytes are not very viable 

 in the allantois and in most cases quickly disappear in the grafted 

 splenic tissue. 



It is a positive tropism between the adult mesenchymal cell 

 and the tumor cell expressed in the phagocytic power of the 

 mesenchymal cell over the tumor cell and the digestive activity 

 of the adult mesenchymal cell which prove to be the direct 

 factors in the disappearance of the tumor cells in a double mixed 

 graft of tumor and spleen. One of the remarkable results of the 

 various experiments undertaken in this direction is the fact, that 

 only the adult splenic mesenchyme, not the embryonic, exhibits 

 the capacity of digesting tumor cells. This observation well 

 corresponds with the fact that the embryo fails to resist growth 

 of heterogeneous tissue. 



I have already mentioned that only in respect to the Ehrlich 

 sarcoma and to the sarcoma 180 could I obtain results which 

 clearly demonstrate the phagocytic and digestive activity of the 

 adult splenic mesenchymal cells. The study of the growth of 

 other tumors and of the check of their growth is sufficiently 

 advanced to enable me to conclude that the inhibition of the car- 

 cinoma growth is effected by a mechanism not altogether iden- 

 tical to that described in relation to the Ehrlich sarcoma cells. 

 Must this fact astonish us? I do not think so. To expect a liter- 

 ally identical response of the mesenchymal cells to different agents 

 would be just as inconsistent as to expect the digestive activity 

 in all multicellular animals to proceed in a perfectly identical 



