434 VERA DANCHAKOFF 



With these problems in view, I began the study of the mutual 

 relationship of mesenchyme and a fast-growing heterogeneous 

 tissue. An objection to the use of embryonic mesenchymal 

 tissue is found in the fact that the tissues of the embryo, in 

 contradistinction to those of the adult, do not offer resistance 

 against heteroplastic grafting. Therefore, it seems rather im- 

 probable that the power of digesting a foreign living cell is an 

 inherent property of the embryonic mesenchyme. 



The relation of adult splenic mesenchyme of the fowl to 

 mouse sarcoma has formed the object of my study, and the 

 allantois of the chick has been chosen as a culture medium, in 

 which the activity of the mesenchyme may be easily followed. 

 The loose structure and rich vascularization of the allantois 

 have been shown to offer to the grafted adult splenic mesen- 

 chyme of the chick conditions favorable not only for the life 

 of its cells, but also for their further growth and differentiation. 

 A recent observation on the growth of the adult splenic tissue of 

 the fowl on the allantois* has shown, moreover, that the phago- 

 cytic activity of the grafted mesenchymal cells of the adult 

 spleen against erythrocytes and occasionally against granular 

 leucocytes of the chick may be extensively revealed in this 

 environment. 



The presence of the small lymphocytes in the meshes of this 

 tissue is a distinctly unfavorable characteristic of the splenic 

 mesenchyme, especially in a study of the bearing of the mesen- 

 chymal activity upon the resistance of the organism against 

 heteroplastic grafting, since the small lymphocyte itself is con- 

 sidered by some investigators to be a factor in this resistance. 

 However, a previous study of the growth of the adult splenic 

 tissue of the chick on the allantois has shown (Danchakoff-*) 

 that the small lymphocytes are not viable within the allantois. 

 They rapidly emigrate from the transplant into the spaces of the 

 allantois where they are frequently seen to disintegrate and to 

 be ingested by the embryonic mesenchymal cells of this organ. 

 At any rate, their presence in the grafted splenic mesenchyme is 

 always easy to detect and take into account. 



