14 B. Benjamin 



approach to some as yet unknown natural lifespan (and it is 

 difficult to separate the two concepts) the present over- 

 simplified analysis may serve well enough. It is indeed argu- 

 able whether the present knowledge of ageing processes 

 justifies a more recondite approach. 



We may, however, discern the possible lines of future 

 development. If it be accepted that ageing is a process of 

 disorganization — the introduction of the random element — 

 then we may apply, as Perks has suggested (1932), stochastic 

 processes to study first the distribution of ages at which 

 organization gives place to disorganization and, second, the 

 distribution of subsequent lengths of life of the group of lives, 

 w^hich at each age are subject to progressive disorganization. 

 A prerequisite is co-operative study by biologists and statisti- 

 cians of available evidence of the age incidence of the dis- 

 continuity between organization and disorganization in 

 animals. This means shifting attention from death to early 

 signs of degeneration in healthy lives under continuous 

 observation. 



Summary 



In the past hundred years or so the peak in the age distri- 

 bution of deaths in the general population has moved to a 

 more advanced age (for men from 72 to 76 years, and for 

 women from 73 to 80), and the proportion of deaths which, 

 on simple assumptions, might be regarded as "senescent" 

 (i.e. of those who attain a predetermined lifespan) has in- 

 creased (for both sexes from about 40 per cent to about 70 per 

 cent). Previous analysis of the so-called "curve of deaths" is 

 reviewed and some suggestions are made for future analysis. 



REFERENCES 



Barnett, H. a. R. (1955). J. Inst. Actu., 81, 105. 

 Barnett, H. a. R. (1958). J. Inst. Actu., 84, 212. 

 Beard, R. E. (1950). Proc. Centen. Assembl. Inst. Actu., 2, 12. 

 Clarke, R. D. (1950). Proc. Centen. Assembl. Inst. Actu., 2, 12. 



