288 



BIOLOGY OF THE LABORATORY MOUSE 



It agrees with the F2 generation results and thus goes far to establish the 

 correctness of the theory used to explain the observed figures. 



In a review of the genetics of tumor transplantation by Haldane (33) the 

 theory herein advanced is accepted. 



Table 8 

 Comparison of Observed and Expected Takes of Tumor 13714BX, Orig- 

 inating IN an Fi Mouse, in Animals Produced by Crossing Fi Mice 

 TO THE Parent Stocks 



More recent experiments by Gorer (29, 30) have provided evidence that 

 in the case of certain transplanted mouse tumors the genes involved have a 

 chemical basis in certain iso-agglutinogens which have been identified. 



Evidence of Mutations in Transplanted Tumors 



Once the principle of Mendelizing units underlying transplantation of 

 tumors was established, a means was provided for interpreting more accu- 

 rately the nature and significance of variations in the number or percentage 

 of successful "takes" in difference generations or experimental groups of 

 mice. 



Utilizing very cleverly selected inbred lines of mice and their hybrids, 

 Bittner (10) was able to explain and to reproduce at will the complicated 

 curves on which the investigators at the Imperial Cancer Research Fund in 

 London had based a theory of fluctuating virulence of the tumor which was 

 supposed to be rhythmic. 



Bittner showed that different proportions of various genetic types was 

 all that was required. There was no need of hypothesizing either fluctuating 

 virulence or rhythm in that fluctuation. 



It was, however, desirable to set up a series of experiments designed to 

 show whether transplantable tumors did change and if so in what respects. 



In order to provide the proper conditions for such a test it was necessary 

 to keep constant the genetic constitution of the various populations studied 

 so that when variation occurred it would be due to some change in the tumor 

 itself. 



