466 VERA DANCHAKOFF 



chymal cell either of allantoic or splenic origin. Other experi- 

 ments have shown that adult splenic tissue submitted for a 

 certain time to a low temperature, but still alive, invariably 

 exhibits a phagocytic and digestive activity against an Ehrlich 

 sarcoma cell. These facts clearly indicate that the prime factor 

 of the encapsulation of the Ehrlich sarcoma cells by a mesen- 

 chymal cell must be attributed to the acquisition of a new prop- 

 erty by the adult splenic mesenchymal cell. Since the contact 

 with substances outside living cells does not make the tumor 

 cell more accessible for an embryonic allantoic or splenic cell, 

 it must be a change undergone by the adult splenic living cell 

 which makes it capable of encapsulating otherwise uninjured 

 tumor cells. 



8. CONCLUSIONS AND DISCUSSION 



The above series of experiments and a detailed analysis of 

 their results lead to the conclusion that the adult splenic mesen- 

 chyme of the fowl has the power of encircling and encapsulating 

 living Ehrlich sarcoma cells in the allantois of the chick and of 

 submitting such tumor cells in the intracytoplasmic cavities so 

 formed to a process of gradual digestion. 



There exists a marked functional difference between the em- 

 bryonic and the adult mesenchyme of the spleen. The adult 

 mesenchyme of the chick spleen has the power of encircling and 

 digesting not only homologous cells, but also certain heterolo- 

 gous living tumor cells (Ehrlich sarcoma and Crocker Fund 

 sarcoma no. 180), which is lacking in the embryonic splenic 

 mesenchyme; this is not, however, the only distinction between 

 the two different stages of the same tissue. Only a graft of adult 

 splenic tissue on the allantois causes granuloblastic transforma- 

 tion of the host's mesenchyme. The embryonic splenic tissue, 

 even though it rapidly undergoes a granuloblastic transforma- 

 tion, will not call forth any notable change in the host's mesen- 

 chyme. This capacity for granuloblastic differentiation is a 

 property common to the splenic mesenchyme of any develop- 

 mental stage and reveals itself under normal embryonic condi- 

 tions in only a moderate degree, but can be greatly intensified by 



