PROLONGATION OF LIFE DUE TO X-RAYS 



TABLE 2 



451 



A further analysis of the data of groups IV to JA will be of 

 interest. The curves shown in figure 1 were each replotted on 

 probability paper^ (fig. 2). It was found that each curve was 

 composed of portions of three accurate probability curves, 

 joined end to end. It is as though there were three causes of 

 death, or perhaps three definite groups of ages. These three 

 portions of the death-rate curve will be termed A, B, and C. 

 Portion C represents those beetles which lived the longest in 

 their group. 



* The ordinates of probability paper are so spaced that the ordinary curve of 

 the probability integral is represented by a straight line. 



