200 Immune Reaction to Transplanted Cancer in the Rat. 



neighbouring connective tissues of the host, and nowhere can there be detected 

 that projection of fibroblasts between the cells of the tumour which invariably 

 occurs in successful grafts. In many cases the fibrin barrier is even more 

 persistent than in the specimen from which the drawing was made. 



After the third day, the graft in a normal animal is the theatre of a 

 progressive and orderly vascularisation and formation of stroma. By the 

 fifth, an acinous arrangement of the parenchymal cells is practically 

 completed, and at the seventh day, the production of collagen having 

 commenced in the new stroma, the implanted tumour is well on its way 

 toward maturity. 



Widely different conditions, on the contrary, obtain in fragments which 

 have been introduced into resistant rats. After the third day, degeneration 

 of the graft becomes progressively more serious, and, in the absence of the 

 specific stroma reaction, necrosis is complete by the tenth, although those 

 cells more fortunately situated at the margin of the fragment are able to 

 survive, and in a few cases even to proliferate, as long as eight days after 

 transplantation. 



The investigation leads inevitably to the conclusion that the phenomena 

 described by Eussell as characterising the immunity of mice to tumour 

 implantation occur also in the case of the resistance offered by rats. 

 Furthermore, as no difference could be detected between grafts taken from 

 rats treated with embryo skin, and those removed from animals which had 

 undergone a previous unsuccessful inoculation with tumour, it is concluded 

 that resistance is similar in the two cases. Both types are the outcome of a 

 failure on the part of the new host to furnish to the implanted fragment the 

 proper blood vessel supply and connective tissue scaffolding. 



The expenses of this investigation were borne in part by the Crocker 

 Cancer Besearch Fund of the College of Bhysicians and Surgeons, Columbia 

 University, New York City. 



