Differences in Transplantable Tumors. 45 



27 (1609) 



Tests for physiological differences in transplantable tumors. 

 By L. C. Strong and C. C. Little. 



[From the Carnegie Institution of Washington.] 



The purpose of this paper is to present a method whereby 

 two neoplasms, that are histologically identical, can be shown, 

 nevertheless, to be different in their physiological reactions. This 

 experiment was begun June, 1920, and is still being continued. 

 Enough data have been accumulated, however, to warrant a 

 preliminary report. 



The tumors employed are two adenocarcinomas of the mam- 

 mary gland, that arose spontaneously in two female mice of a 

 closely inbred strain, the second one arising some three weeks 

 after the first. The mice have been rigidly inbred, brother to sister 

 matings, for about eleven years. One would expect, in that time, 

 that the strain must have become homozygous in all, or nearly all, 

 genetic factors that no doubt underlie morphological and physio- 

 logical characters. This conclusion is warranted by evidence 

 obtained from implanting bits of the two tumors into mice of this 

 strain. The trochar method of implanting the neoplastic tissue 

 has been employed throughout the experiment. In this pre- 

 liminary experiment both tumors grew in 100 per cent, of all 

 mice inoculated, irrespective of whether the two tumors were 

 inoculated into the same mouse or into separate individuals. In 

 case the two were inoculated into the same animal, the first 

 (dBrA) was always inoculated into the right axilla, the second 

 (dBrB) into the left axilla. The growth curves for each were 

 charted from weekly observations. There was apparently no 

 effect of one tumor upon the other when growing in the same 

 mouse, either in percentage of indications or rate of growth. 

 They remained entirely distinct. The question naturally arose, 

 "Are the two tumors actually identical?" 



The complexity of the genetic factor system that evidently 

 underlies susceptibility to transplantable tumors makes it highly 

 improbable that two identical tumors could arise independently 

 within three weeks of each other, even in the same relatively 

 homozygous strain of mice. 



