258 H. J. CURTIS AND CATHRYN CROWLEY 



cuKTis: Well you can certainly say that there is a correlation between the numbers of 

 abnormalities that are produced and the age of the animal. Here is a phenomenon which 

 is age-dependent and we know that — shall we say — that ageing process is age-dependent. 

 So that there is that correlation I think, but I certainly agree with you that it's indicated 

 very strongly that there must be other important factors commg in which may be of 

 dominant importance. As a matter of fact I hope to give some further evidence later this 

 afternoon as to what some of these other factors are. 



mole: If 3'ou got 50% or 70% mitotic abnormalities as a resiilt of X-rays, and just 10% 

 more in the controls after your chemical and the hfe-shortenmg wasn't very different 

 between those two then surely your evidence has no bearing on life-shortening. 



