Behavior of Mixtures of Tumor and Embryo. 73 

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The behavior of transplanted mixtures of tumor and embryo. 



By PEYTON ROUS. 



[From the Laboratories of the Rockefeller Institute for Medical 

 Research, New York.] 



Mixtures of hashed mouse-embryo and transplantable mouse- 

 tumor were inoculated into the subcutaneous tissue of adult 

 animals. It was found that growth of both elements took place, 

 often in intimate association. But to obtain these results a 

 balancing of avidity was necessary, such as Apolant used in 

 his mixtures of sarcoma and carcinoma. Only tumor-cells of 

 sluggish character can be implanted with the embryonic cells, 

 which otherwise are outgrown and soon die. This is interesting 

 in view of the enormous proliferative ability of the embryonic cells 

 in titero, and it would seem to show that such ability depends at 

 least as much on the excellent nutritive arrangement in utero as 

 on inherent cell-energy. The transplanted cells not only lack the 

 power of unlimited growth that characterizes tumor, but during 

 their temporary growth in a new environment lack the proliferative 

 energy that many tumors show. 



In a mixed graft that has only partially succeeded, tumor and 

 embryo tend to grow or fail together. This must be largely a 

 matter of immediate nutritive conditions, which are best, for 

 example, at the edge of the graft. But it is also notable that at 

 those points where one element has elicited a supporting reaction 

 from the host tissues and is growing, the other has also succeeded. 

 When the tumor mass is walled off from the host by a layer of 

 developing embryo, it nevertheless grows, utilizing as stroma the 

 embryonic connective tissue. 



In a number of quantitative experiments it was found that 

 tumor and embryo succeed better alone than when mixed. This 

 difference is at first not marked. Later, when the embryonic 

 element of the mixed graft, after its short period of development, 

 breaks down, more or less of the tumor is involved with it. 



It was observed not infrequently that the embryonic epithelium 

 and the carcinomata united when they met during the process 



