464 VERA DANCHAKOFF 



The comparison of the results of these two experiments does 

 not, therefore, necessarily imply a change within the splenic 

 adult mesenchymal cell. The splenic adult mesenchymal cell 

 may remain identical in its functional capacity, as it does in its 

 developmental potenciefi. The encapsulating and digesting 

 process to which the tumor cell is submitted in a tumor-adult 

 spleen graft would then be determined by a change undergone 

 by the tumor cell, which, though morphologically inappreciable, 

 would nevertheless exert on the otherwise unchanged mesen- 

 chymal adult spleen cell a chemotactic effect. In short, the 

 problem reduces itself to the following: Is the encapsulation 

 of the tumor cell by adult splenic mesenchyme due to a definite 

 property of the adult splenic cell acquired by the adult in con- 

 tradistinction to the embryonic cell, or are the changes of the 

 tumor cells primarily dependent upon the effect of extracellular 

 substances developed in the organism in later stages and pres- 

 ent in the adult spleen, but possibly foreign in their origin? If 

 submitted to the influence of such hypothetical substances 

 which might be present in the adult splenic tissue, will the tumor 

 cell then exert upon the embryonic mesenchymal cell a chemo- 

 tactic action, resulting in the encapsulation of the tumor cell 

 and its subsequent digestion? Another series of experiments 

 was made to clarifj^ this question. Ehrlich sarcoma was mixed 

 with a mash of sterile adult splenic tissue, which had been pre- 

 viously kept frozen, or in a refrigerator for from three to seven 

 days, or in the incubator from one to three days, which, if grafted, 

 would not ta"ke. It was expected that if injurious substances were 

 present in the splenic tissue outside the living splenic cells, the 

 tumor cells might be altered in this case in the same way as 

 in the mixed tumor-adult splenic grafts, and that in such a case 

 the embryonic mesenchymal cells of the allantois itself would 

 begin the encapsulation of the tumor cells. Study of such grafts 

 has, however, shown that the tumor grew without showing any 

 injurious effect from the presence of the necrotic adult splenic 

 tissue. The allantoic mesenchymal cells exhibited intensive 

 phagocytic activity against the necrotic particles of the adult 

 splenic tissue, but respected the living Ehrlich sarcoma cells. 



