246 General Discussion 



increased the expectancy of life, but such an influence was not apparent 

 if a similar diet was fed to animals after maturity. There was discussion 

 as to whether the duration of the reproductive phase might have a 

 bearing on tlie length of life. It is difficult to draw conclusions from 

 human data, but comparative biological studies do not support such a 

 hypothesis. 



Prof. Lewis stressed the need for longitudinal studies. The statistical 

 method has its value, but it also has its limitations. We need to have 

 longitudinal studies, because only so can we correct many of our early 

 impressions and assess more accurately the factors concerned. The same 

 point was made with regard to the assessment of function by Sir Frederic 

 Bartlett. Adaptability may so easily occur and lead to misinterpretation 

 of results. Prof. Le^\^s, however, showed that many of our tests are often 

 geared to a certain time or age period. We carry out studies on a few 

 medical students and a couple of staff members, draw a graph and derive 

 our constants. It is necessary to realize that there are peak performances 

 for most functions, and there may be varying rates for attainment and 

 for the maintenance of such peaks. We did not quite agree that there 

 was necessarily a uniform steady percentage decrease from the peak 

 performance with age; this w ould of course introduce a further variant. 



When we come to studies in man we are up against the question of 

 environment, which in turn introduces the factors of disease and of 

 impaired reserve. Prof. Christie showed very clearly that in the lungs 

 there is a decrease in functional capacity, whether due to the onset of 

 incipient emphysema, to loss of elasticity, or to what you will (he was 

 careful not to decide which). The process is certainly different from those 

 associated with ordinary pathological changes, and therefore one vital 

 function would appear to show some decrease with age which is not 

 entirely conditioned by the environment, in this case the fixity of the 

 chest wall. 



There is the question of the role of continuous trauma, or even normal 

 activity. We usually think that normal activity is healthy and good, 

 and can continue without harm, but are we right in this? In this country 

 as you all know we are much concerned about the recent dissolution of 

 certain of our aeroplanes. A novelist suggested metal fatigue as a possible 

 cause of air disasters, and Dr. Parkes hinted indirectly at similar 

 possibilities in his experiments on freezing. 



I end on an imaginative but provocative note. We know that when an 

 organ is removed from a composite organism and given the opportunity 

 in a good environment, it may live longer than it is known to live in the 

 composite organism. If we could keep a cell or organ in a perfect 

 environment, would such an organism live indefinitely? In other words, 

 might the photograph Dr. Parkes showed [Frontispiece — Ed.] be a clue — 

 could in fact the wear and tear we call senescence really be due to a 

 biophysical dissolution? 



We need not be gloomy about ageing. Sir Frederic Bartlett gave us 

 much hope that we might adapt, and adapt well, to new standards. We 

 were certainly given hope from the functional viewpoint that we could 

 anticipate leading very full and active lives whatever our allotted span 



