56 General Discussion 



In the first group of organs decrease of adaptation begins when there 

 are no more tissue reserves left. Tliis occurs normally very late in 

 human life. It is the main problem to be studied in gerontology. In the 

 second group of organs decrease of adaptation begins when the regenera- 

 tion process slows down in old age. When both these aspects appear 

 together age begins to be visible. 



Now a few words on arteriosclerosis which is one of the chief problems 

 of gerontology. We know that arteriosclerosis may start in early 

 childhood and increase during life. I think that arteriosclerosis is 

 not a cause of ageing but it becomes intensified by the ageing process 

 because it is a summation effect of very different aetiological factors; 

 therefore it must be discussed together with all the problems of ageing. 

 In arteriosclerosis it is possible that the tissue reserve diminishes as a 

 consequence of anoxaemia. In arteriosclerosis we have to distinguish 

 between two types, according to the width of the vessels: 



1 . The vdde type occurring often in vessels wliich have an appearance 

 like tubes of cement but causing no organic complications whatsoever. 



2. The narrow type: here the arteriosclerotic changes are very small 

 local patches in one part of a coronary artery causing local stenosis. 

 The consequences may be very serious. In young people we generally 

 find the narrow type, in old people usually the wide one. Therefore the 

 arteriosclerotic syndrome depends on these two different types which 

 ought to be distinguished. 



Miescher: When discussing the ageing process, a kind of vitality factor 

 should be taken into account — ageing in its declining phase is 

 characterized by decreasing resistance capacity of the organism to 

 outer and inner injuries in connection with its declining level of vitality. 

 The living organism is an open system staying in a dynamic or flowing 

 equilibrium of assimilative and dissimilative processes. It is constantly 

 threatened by outer and inner injuries (I) and is protected by an inner 

 resistance capacity (R). Three possibilities can be distinguished. There 

 is no ageing when: 



(a) I = R, that means immortality. 



(b) I > R, I and R constants. 



In a whole population an exponential decline of survivals but no real 

 ageing A\'ill occur: 



X = Ae -kt (or kt = In A — In x) 



e = basis of natural logarithms 



t = time 



x = number of survivals at time t 



A = number of survivals at time O 



k = rate of destruction 



There is ageing when: 



(c) I > R, I constant, R declining (e.g. following an 



exponential course) 

 X = Ae -kte"* (equation of Puetter, 1921) 



a = ageing factor (rate of ageing). 



k = destructive factor (rate of destruction) 



