PLATE 1 



EXPLANATION OF FIGURES 



1 Section through a part of Ehrlich sarcoma graft grown four days on the 

 chick allantois. Tumor cells loosely arranged at the periphery of the graft and 

 proliferating intensely. The small embryonic allantoic mesenchymal cells and 

 vessels grow between the groups of tumor cells Al. Ms., allantoic mesenchyme; 

 c, capillary; Tc, tumor cells. 



2 A section through an Ehrlich sarcoma graft which remained separated by 

 the serosa from the allantoic mesenchyme, forty-eight hours after grafting. 

 Most of the tumor cells, Tc, show a normal structure and two are seen in mitosis, 

 one of them has ingested two mouse erythrocytes; M. ere, mouse erythrocytes still 

 well preserved. The endothelium of the mouse vessel M. vs. is in regression. 



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