4 8 



Scientific Proceedings (iio). 



first three week periods differ significantly in the two tumors, the 

 difference in each case being more than three times its probable 

 error. The slight rise in the curves in the last two periods is not 

 real but due to the dying off of some negative individuals during 

 an epidemic. The last three points approach mathematical 

 significance and possibly will be significantly different when more 

 numbers are obtained. Since both curves are approaching zero 

 there would be convergence. For that reason the difference be- 

 tween corresponding points would not be as great as between 

 points at the other end of the curve. 



We are, therefore, led to the conclusion that the two histolog- 

 ically identical tumors possess different physiological reactions. 

 Wherein lies this difference? This cannot be explained by 

 fluctuations in the tumor cell. Within insignificant variation 

 limits, the two tumors have retained their own reaction poten- 

 tiality throughout the whole experiment. 



Physiological differences of tumors of the same general type 

 may, therefore, be independent of histological differences. There 

 are two remaining explanations, either (a) cytological or (b) 

 genetic. The cytological explanation involves fluctuations from 

 the normal type of mitosis, amitosis, etc. Such explanations are 

 not wholly acceptable to the investigators who approach the tumor 

 problem from another angle. 



We are led to the conclusion that it is in the genetic constitu- 

 tion of the individual that we are to look for the underlying causes 

 that undoubtedly determine susceptibility to transplantable tumor 

 tissue. 



It has long been recognized that tumor cells are not distinct 

 from normal cells. They only differ in their ability to grow 

 indefinitely. Since normal tissues are, to a large degree, dependent 

 upon the genetic complex of the individual, may we not also look 

 for the causes underlying susceptibility to transplantable tumor 

 as being similarly correlated with genetic factors? 



We are indebted to Drs. James Ewing and H. J. Bagg of the 

 Memorial Hospital, New York City, for their kindness in analyzing 

 the material histologically. 



