116 LEONELL C. STRONG 



tomized individuals when all age groups are considered. The 

 primary effect of gonadectomy is not the changing of the per- 

 centage reactions, but that some few individuals are then able 

 to grow the transplanted tissue progressively. This question 

 will be taken up later in the General Discussion. 



p. 'Adaptation.' The following experiment has to do with a 

 supposed peculiarity of the tumor cell, namely, that of its ability 

 to adapt itself to a foreign environment (host). The tumor tis- 

 sue derived from gonadectomized individuals was inoculated 

 into normal and into other gonadectomized individuals of the 

 wild house mouse. Figure 33 includes the susceptibility curves 

 for both the normal dBrB tissue and for the dBrB tissue that 

 had already succeeded in growing for at least eight to ten weeks 

 in wild individuals (gonadectomized). 



In order to increase the number of observations in one com- 

 parison, both normal and gonadectomized individuals are in- 

 cluded in a single curve. 



Normal dBrB (ndBrB) 1768 negative : 137 reactions ±7.62 or 7.19% ± 0.40 

 Adapted dBrB (adBrB) 386 negative : 27 reactions ±3.39 or 6.54% =b 0.82 



Difference 1.06% ± 0.92 



The difference is thus 1.15 times its probable error 



There is no significant difference between the potency of the 

 normal dBrB tumor cell and the 'adapted' dBrB tumor cell. 

 In other words, when a relatively homogeneous race of mice has 

 been employed, the phenomenon of adaptation (or virulence, 

 for that matter) is not seen. The special 'A' tumor does not 

 show any particular adaptation. This will be discussed later. 

 If there is any difference (however slight) between the two reac- 

 tions, it is in favor of the normal dBrB tumor that had never 

 grown in wild house mice. 



The evidence against the theory that a transplantable tumor 

 possesses variable powers of adaptation derived from the use of 

 the dBrA tumor is not so conclusive, but bears out the general 

 result obtained from the dBrB tumor. A total of three dBrA 

 tumors have grown in wild mice. The first one in the normal 

 adult male W238 referred to previously and the other two in 

 gonadectomized individuals (one a male, the other a female). 



