SUSCEPTIlilLITY TO TRANSPLANTABLE TUMORS 117 



Fortj''-five wild mice were inoculated with the three tumors. 

 Not one of these mice ever grew the tumor progressively. Un- 

 fortunately, the tumor in this case was inoculated into the iUac 

 region. It was found too late that this region is unsuited for the 

 palpation of small masses, so that the end result alone can be 

 utihzed in reaching a conclusion for the dBrA tumor. 



Probably, neither tumor, therefore, possesses the power of 

 adaptation when inoculated into a relatively homogeneous non- 

 susceptible race. 



III. GENERAL DISCUSSION 

 1. Value of proved stocks 



Several results here recorded are quite distinct from those 

 usually obtained in experiments dealing with transplantable 

 tumor tissue. Since we have used as homogeneous a race of 

 mice as is at present available, it seems that the conflicting re- 

 sults of other investigators in this field must have been in a large 

 degree due to the different kinds of mice that they employed. It 

 has already been demonstrated (Little and Tyzzer) that the sus- 

 ceptibility to transplantable tumor tissue depends on a complex 

 of mendelian relations. That a mouse will grow the transplanted 

 tissue progressively is as much the result of the genetic consti- 

 tution of that mouse as it is of any inherent characteristic of the 

 tumor cell. Both these factors, however, must be taken into 

 consideration for the determination of the final outcome of im- 

 planting a bit of tumor into a given mouse. 



Investigators, as a rule, have neglected the host factor. Most 

 of them still maintain that the host employed is of only second- 

 ary importance. 



Doctor Woglom, in a recent pubhcation on ''Virulence of 

 Adaptation," evidently witnessed a phenomenon similar to that 

 seen by us in our first experiment (figs. 2 and 5). This is the 

 fact that apparently identical neoplasms (derived from multiple 

 mammary carcinoma primarily) have different reaction poten- 

 tialities when inoculated into mice from the same dealer. He 

 described this difference to the presence or absence of the power 

 of adaptation on the part of the tumor cell; different tumor cells 



