11 



88 Discussion 



Berg: We do have adrenal weights but we have not studied them 

 in relation to time of onset or incidence of lesions. 



Comfort: Do these rats appear to produce more cortisone than the 

 ordinary animal of that size ? 



Berg: I do not look upon these restricted animals as being under 

 stress. 



Comfort: Even if you spend your life in a deck chair, dietary 

 retardation is still a physiological stress. These animals have less to 

 eat than they would normally have — although wild rats do not 

 get all they want to eat. 



Berg: Within certain limits a state of hunger in the restricted 

 animal appears to be nearer normal for the rat than the satiety of 

 the ad libitum-fed rat. 



Comfort : It is still possibly a stress. The domestic rat is the result 

 of selection for equanimity and low adrenal weight. Wild-caught 

 rats are quite unmanageable. We have got laboratory animals 

 which, whether we like it or not, have been adapted by covert 

 selection to living under conditions of captivity. 



Berg: We have in progress stress experiments based on variations 

 in light, noise, and other unfavourable conditions. The adrenal 

 weights of these rats will be compared with the adrenals of rats 

 under standard conditions. 



Tanner: Maynard Smith asked about the possible common 

 mechanism whereby the times of incidence of these various diseases 

 could all be brought forward together. I think that is rather a dif- 

 ferent situation from the amyloid disease one. As Comfort said, this 

 somewhat nebulous concept of stress does provide a basis. I have 

 recently been to the Mental Health Research Fund conference on 

 "Stress in relation to mental health and disorder" at Oxford (1959. 

 BlackweU's Scientific Publications, in press). Prof. Hans Selye was 

 there and talked about stress as almost equivalent to ageing. The 

 two concepts were being pushed very close together. Selye dis- 

 cussed some very interesting data on the effect of myocardial 

 degeneration of various balances of deoxycorticosterone-type 

 hormones and cortisol-type hormones. He evidently regarded the 

 ordinary circulation of the blood as constituting a stress, while we 

 would regard it as something which perhaps produces ageing. It is 

 particularly in such endocrinological regulations that the general 

 mechanism Maynard Smith is querying probably lies. 



Sacher: Ionizing radiations, which are normally deleterious and 

 shorten life, can in some circumstances increase life expectation, 

 although without increasing the maximum lifespan. When this 

 occurs in mice and rats, it is observed that the infectious diseases 



