204 General Discussion 



to 18 or 19 g. and were large round si)heres, so heavy that they couldn't 

 walk. However, so far as I remember, the age at maturity didn't 

 appear to have been altered. 



Verzdr: I think we have again reached a very basic question of old 

 age research, which is the question of organization. If we want to get on 

 with the problem of whether nutrition influences ageing, statistical 

 analysis is probably impossible. As Prof. Brull has said, it would only be 

 possible to use animals, but if you use animals you really can't compare 

 with hmnan nutrition. Perhaps this conference could propose an 

 organization which could keep up continuous research on ageing on a 

 definite group of individuals. 



Cowdry: I agTce with you heartily, and it seems to me that while we 

 can't carry research through the earlier years of life, we could through 

 the Veterans Administration carry it through the later years, from early 

 maturity right to the end. It is one hope of the Third International 

 Gerontological Congress, which is about to take place, that we will try to 

 establish methods of physical examination on both sides of the Atlantic 

 that will yield results that can be properly compared, in these large 

 groups of population always receiving free medical attention. 



Comfort: One point about longitudinal studies, arising from what both 

 Prof. Medawar said and what Prof. Verzar said, is the difficulty I think 

 we shall encounter in using landmarks like the menarche. I understand 

 that in a mixed population which is not genetically homogeneous one is 

 quite possibly going to find that it is the rapid developers which are the 

 longer livers, as is the case with hybrid vigour. Perhaps the situation, 

 if we do longitudinal studies, won't really be analogous to that which 

 you get if you take a fairly uniform population of rats and divide them 

 into two groups and run them against each other. 



McCay: That is a very important point, which should be stressed. If 

 one takes a group of rats and compares the very slow growing with the 

 very rapidly growing, it is similar to taking a population in which one 

 has let us say teenagers with tuberculosis who are growing slowly, and 

 who are condemned to an early death unless the tuberculosis is checked. 

 One will always have some diseased animals that will tend to grow very 

 slowly and die early. There has been quite a bit of confusion with 

 regard to the effects of retarded growth amongst a group of rats of that 

 type, where one has diseased and healthy animals. 



Comfort: It was particularly brought home to me by seeing some 

 figures some of my colleagues have got in the case of rate of growth and 

 rate of development in mice of hybrid and inbred lines. There, in the 

 case of the vigour, you get heterosis; it is perfectly clear that early 

 development goes with longevity and with long reproductive life. You 

 get the sort of mouse (I think it was one of Gates's crosses) that breeds 

 earlier than anybody else's mouse and also seems to live longer and goes 

 on breeding longer than anybody else's mouse. Unless we know what 

 the genetic composition of our population is, we may be misled by that 

 sort of effect. It is, I imagine, possible to breed both an early developer 

 and an unusually vigorous individual if you have the right degree of 

 heterozygosity. 



