OLD AGE AND NATURAL DEATH 



statistical picture of the magnitude of this predisposition. 

 Many sciences use a picture of this sort, and some use no other; 

 the problems it raises are interesting, but not at the moment 

 relevant. 



Minot wanted to bring not merely size but shape as well 

 within the ambit of his laws; but complained, as many have 

 done since, that ""we do not possess any method of measuring 

 differentiation which enables us to state it numerically\ Such 

 attempts as have been made to do so support his theory; for 

 example, the rate of change of shape of the human being falls 

 off progressively through life.^ But we do know that Minofs 

 laws are by no means commonly true of faculties other than 

 those which turn upon the pattern and the rate of growing. 

 The sort of sensory, motor and ''mentaP tests that are used to 

 measure physical and intellectual prowess usually give their 

 best values in the neighbourhood of the age of twenty-five, or 

 later. Usually, but not always: it is around the age often that 

 hearing of very high-pitched sounds is most acute. ^ Information 

 of this sort is intrinsically important, for it does something to 

 confirm a theorem of wide significance which many clinicians 

 have long taken for granted — that the time of onset and rate of 

 ageing of the faculties and organs may vary independently 

 within fairly wide limits. Other evidence tells against it. One of 

 the most useful lessons to be learnt from the natural historian"'s 

 studies of animal longevity^ is that the life span varies greatly 

 in length between quite closely related types of organism. What 

 can this mean, if not that the ageing process in the individual 

 as a whole is geared by one or two limiting or '"master"' factors? 



Minot ""s special theory of the ageing process is just as un- 

 usual as are his general laws, for he believed that cellular 



1 P. B. Medawar, Proceedings of the Royal Society. Series B, 132, p. 133, 

 1944. 



2 Y. Koga and G. M. Morant, Biometrika, 15, p. 348, 1924. Cf. the data 

 summarized by V. Korenchevsky: Annals of Eugenics, 11, p. 314, 1942. 



^ The most important of these are by S. S. Flower. See note 2, p. 32. 



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