436 VERA DANCHAKOFF 



stages after grafting, and a peculiar reaction invariably was 

 developed in this region by the splenic mesenchyme, which 

 strongly reminds one of the phagocytic activity of a macrophage. 

 The phagocyte in this case is not a single cell, however, but a 

 mesenchymal syncytium with a common cytoplasm and numer- 

 ous nuclei; the object of attack is the living cell of a mammalian 

 tumor. As a result of this reaction the tumor stops growing at 

 the place of contact with the splenic tissue, although it grows 

 well in contact with the loose mesenchyme of the allantois. 



Is this mesenchymal reaction to be interpreted as a result of 

 a mere local interaction between adult splenic mesenchyme and 

 cells of the Ehrlich sarcoma and is the allantois of the embrj^o 

 therefore no more than a culture medium? Or does the embryo 

 itself, at whose expense the graft is growing, enter as a factor 

 into the results obtained? The fact alone that the reaction 

 develops only in the strictly limited region in which both tissues 

 come into contact and does not extend to the whole tumor seems 

 rather to make the participation of the host as a factor in this 

 reaction doubtful. 



In order to extend the mesenchymal reaction to the whole 

 tumor graft, both tissues were brought into more intimate con- 

 tact. Crushing splenic and tumor tissues together and mixing 

 them carefully gives an intimate contact of the two kind of cells. 

 A preparation of such a mixture shows small particles of the 

 tumor tissue enveloped by strands of splenic mesenchyme, the 

 latter occasionally appearing in the form of small islands. Such 

 a mixture of both tissues was used as a grafting material and the 

 progress of the growth of these double grafts was followed day by 

 day. This series of experiments has been repeated five times 

 on sixty eggs, with invariably identical results, described in section 

 5. Moreover, such series of experiments have been repeated 

 through a period of eighteen months on smaller groups of eggs. 

 Though an attempt has been made to ascertain whether the 

 connective-tissue cells in other regions of the body were capable of 

 exercising a similar digestive activity against the Ehrlich sarcoma 

 cell, no definite results have yet been obtained. 



