A Study of Aging, Thermal Killing, and Radiation Damage by Information Theory 303 



The assumption of Section II concerning the nature of pC//^, A) is retained and 

 the expression for the surxiva! curve is: 



log. Ilk = P(^.^ ^) 



//o-^. + i>;/Hoiog2/'ay) 



^,} 



(9) 



That some survivorship curves have wholly or substantially the form of 

 equation (9) for normal aging where A is the time can be shown for a wide 

 variety of organisms. Some examples are shown in Fig. 2 and also one in 



II 27 43 51 59 67 75 83 91 WEEKS • 



(TIME UNIT ) AS INDICATED 



Fig. 2. Survivorship curves for two insects and two mammals plotted against the 

 square of the age (see equation (9)). Straight lines for pure vestigial Drosophila 

 (35) obtained from maximum likelihood estimate. Other straight lines are for 



comparison only. (See text.) 



Fig. 3. The data for pure vestigial Drosophila are from Pearl and Parker (35) 

 and represent a life table. The animals are kept under ideal conditions and the 

 number which die in certain time intervals is recorded. All data on Fig. 2 and 

 Fig. 3 are obtained this way. The curve has been fitted by these authors to a 

 function of the following form where a, h, c, d, e are positive constants. 



log / = €"^6 - cA + d?? - e)?) 



(10) 



Pearl and Parker were aware that this description involves too many con- 

 stants and that irrelevant statistical fluctuations are preserved by equation (10). 



