242 General Discussion 



Franklin: No, I think it is straightforward as it stands [see p. 31, Ed.^. 

 But I should hke to say that I am glad you have tackled this problem 

 because we should otherwise be like the negro who was chased by a bear 

 and, asked by someone, when he was going at full speed, Mhere he was 

 going, said "Ah ain't goin' nowhere, Ah'm comin' away from some 

 place". 



Shock: Does a definition of ageing have to be limited to decreasing 

 functions? 



Franklin: Change of function, surely. 



Cowdry: Yes, it can be increasing. 



Krohn: Well, that is the meaning of ageing, isn't it? You use the word 

 "ageing" to mean any change as the organism gets older. You have to 

 use perhaps "senescing" for deteriorative changes. 



Cowdry: I have a definition. Ageing is change with time in the life 

 cycle. 



Lansing: Would you care to qualify that and make it change with time 

 in the adult organism? 



Cowdry: No. 



Krohn: When would you define somebody as having reached adult- 

 hood? 



Lansing: When he has reached maximum size. 



Gross: There should be a distinction between development and ageing. 



Comfort: In Prof. Medawar's temporary absence I would like to put in 

 a plea for his definition of senescence, as the increase in liability to die 

 with advancing age. It may be proper to distinguish ageing from senes- 

 cence, but in that case I think we can scrap ageing altogether and call it 

 development, because gerontology is an entity which only comes into 

 existence to describe a process human beings don't like, a deteriorative 

 process, and I take it that it is senescence with which we are concerned 

 here. Earlier in the meeting Dr. Lansing made a declaration of faith on 

 the subject of the overall unity of the senescent process. He said that we 

 ought to look for underlying processes which explain all senescence. Up 

 to a point I think that that is so, in that I have no doubt that the 

 exhaustion of enzyme systems in cells which don't divide might provide 

 us with something of the kind. But if we do accept, as I suggest we 

 should, the idea of senescence simply as the increasing liability to die 

 with increasing age, then the most striking thing in comparative studies 

 is its diversity. We have insects in which the mechanical wearing out of 

 the cuticle appears to be an important feature, we have others which 

 don't feed at all and appear to deplete their reserves, and we have some 

 animals, as has already been mentioned, which die automatically after 

 breeding, possibly from depletion; we have the elephant, which, I'm 

 told, dies in the wild state when its teeth wear out. I have no doubt 

 that if you gave the elephant false teeth, he would die of some other 

 senescent process eventually. I don't want to speak out of turn, but 

 I'm somewhat sceptical of this underlying unity of any ageing process; 

 I think we should be empirical about it, and treat senescence simply as 

 a name for that whole group of causes which make animals have a 

 determinate life-span instead of an indeterminate one. 



