206 VERA DANCHAKOFF. 



different tumors, but only the Ehrlich sarcoma, and the tumor 

 known at the Crocker Fund Laboratory, under the number 180, 

 gave demonstrable results. It is known that mammalian tumors 

 may be grown easily on chick embryos, but not on adult animals. 

 Also normal adult chick tissue grows well on embryos of the same 

 species. Therefore, embryonic tissues, more particularly the 

 chick allantois, have been used by me as a culture medium, to 

 bring together mammalian tumors and various adult chick 

 tissues. It was expected that the study of the interaction of the 

 tissues of the adult naturally immune fowl and of the mammalian 

 tumor cells grown in a culture medium, for both equally favor- 

 able, might show whether the digestive capacity of the tissues 

 more particularly that of the adult splenic mesenchymal cells may 

 in any way be connected with the resistance offered by the adult 

 animal to the grafting of the tumor on it. The experiments 

 have shown that the Ehrlich sarcoma gives invariably a good 

 growth if grafted alone, but if grafted in a mixture with the 

 spleen, disappears even after a short period of proliferation. The 

 short-lived fame of the small lymphocytes thought to be re- 

 sponsible for this disappearance is still in our memory. Only an 

 absolute disregard of microscopical findings can explain how 

 microscopical pictures similar to thor.e shown here (Figs. I, 2, 

 3 and 4), have been overlooked and how the small lymphocyte 

 could become the fetish of the immunity. 



Microscopical preparations, as seen in retouched photographs, 

 which accompany this paper, illustrate in a striking way the 

 process of disappearance of tumor foci surrounded by the adult 

 splenic mesenchyme in the allantois. Two lines of activity are 

 observed in the mesenchyme, it splits off numerous mobile cells 

 of hemoblastic nature which differentiate further into granular 

 leucocytes. This developmental potency is exhibited in an even 

 more intensive way by the splenic adult mesenchyme, if the 

 splenic tissue is grafted alone on the chick allantois. But the 

 fact of grafting the splenic tissue together with tumor reveals 

 in it a new potency and this is its power of isolating and surround- 

 ing tumor cells, of enclosing them in vacuoles and of digesting 

 them within these vacuoles (Figs. I, 2, 3 and 4). The adult 

 splenic mesenchymal cell is apparently attracted toward the 

 mammalian tumor cell. Contrary to the embryonic mesen- 



