General Discussion 249 



that Rhinolophus ferrum-equinum and Miniopterus schreibersi could 

 reach at least 14 and 15 years! 



Wislocki: Then you believe that one can prolong the life ex- 

 pectancy of a mammal by reducing the metabolism ? 



Bourliere: I think so. 



Krohn : Have attempts been made to keep animals, that normally 

 hibernate, out of hibernation during each ordinary hibernating 

 period? Would that shorten their life-span? 



Bourliere: As far as I know that experiment has not been done. 



Krohn: That would be relatively easy to do. 



Parkes: The trouble is, I think, that not enough is known about 

 the hibernating mammals to know what their life-span would be 

 without hibernation. 



Krohn : We know little about the natural life-span of any animals, 

 come to that. 



Wislocki: It could, perhaps, be fairly readily found out with a 

 colony of hamsters. 



Parkes: I suppose, yes, if they could be frozen for a significant 

 time. 



Wislocki: If one group could be induced to hibernate to the 

 maximum degree during their lifetime and another group kept 

 active so that they could not hibernate, one might discover whether 

 there was any significant difference in their life-spans. 



Parkes: You have to do that by adjusting the temperature during 

 the winter probably. The laboratory hamster here becomes sleepy 

 and ceases to breed in the winter but it does not go into a proper 

 hibernation. I can see technical difficulties there. 



Williams: It does not necessarily stop breeding either, I think. 

 Certainly in some of our colony we have been selecting those for 

 winter breeding; you can do that. 



Yemm : It seems to me that there is some difficulty in terminology 

 and that we should make the term ' ageing ' apply to the life-span of 

 an organism and the term ' senescence ' apply to parts or tissues of 

 the organism. When it comes to plants, at one and the same time 

 and in the same organism, you may have tissues which are em- 

 bryonic or meristematic in nature and tissues which are senescent 

 in nature ; both of them contribute to the development and activity 

 of the organism. It seems to me that in higher organisms, where 

 there is such extreme physiological specialization, it would be a 

 useful discipline to reserve the term 'ageing' for the organism as a 

 whole, as a chronological relation in its development and ontogeny; 

 and 'senescence' as a term referring to the physiological condition 

 of its different tissues or organs. 



Villee : I think that is a very good point. Prof. Montagna's figures 



