General Discitssion 207 



evidence for an age change in basal metabolism disappears*. So I am 

 inclined to question whether there is an actual slo\\ing of the cellular 

 metabolism as you get older. I think tlie droj) in oxygen consumption 

 which we all see is simply a reflection of the loss of fimctioning cells and 

 their replacement with other non-mctal)olising or at least slowly 

 metabolising tissues. 



Cowdry: However, it used to be thought that there was a significant 

 dehydration, reduction in amount of water per unit of weight in older 

 tissues. And then Hastings and others came along and seemed to show 

 that this was not the case. What is the situation now? 



Shock: 1 think there is no question but that the total water content of 

 the animal decreases with age. Using anti-p>Tene as an index we have 

 found an average change from 34-6 1. to 29-7 1. between the ages of 

 forty and ninety years. Again, if you want to indulge in some fancy 

 assumptions, you can show that this is a loss of functioning protoplasm, 

 because the extracellular water phase does not change significantly, at 

 least in our group of subjects. Tiiis is probably a physiological reflection 

 of the histologically observed loss of numbers of cells with increasing 

 age. 



McCance: I don't know anything about the water, but if you starve 

 a person over eighty he derives exactly the same percentage of his 

 basal calorie requirements from breaking down of his own tissues as a 

 young adult does. So right on into old age that balance seems to be 

 preserved. 



Coivdry: Can you say that the basal metabolic rate in females is in 

 general somewhat lower than males, for the same age, and that that is in 

 some way related to increased life span? 



McCance: Our work has all been done on old men, and I'm afraid I 

 can't tell you anything about old women. 



McCay: There is no proof of any sex difference in any animal other 

 than man. 



Cowdry: Tliere is a difference in man, isn't there? 



McCay: Apparently, yes. 



Shock: But the female has more fat on her from the start, so that this 

 may again be a question of relative amounts of fat. Unfortunately we 

 have never done any studies on women, and I'd like to know if one were 

 to relate oxygen consumption with body water, whether there would be 

 any sex difference left. 



Sinclair: I think Ancel Kej^s has concluded that tliere is no sex 

 difference in terms of active metabolising tissue — it is that there is more 

 fat. 



Cowdry: But there would be a difference in terms of total weight? 



Sinclair: Yes, of course. Or surface area. 



Briill: May I remind you that at the first International Conference on 

 Gerontology I reported that we had started a study of the influence of 

 nutrition and feeding on the ageing of inbred mice. We started this 



* Shock, N. W., Yiengst, M. J. and Watkin, D. M. (1953). J. Geront., 8, 338. 

 See also : Shock, N. W. in Symposium on Problems of Gerontology, 

 National Vitamin Foundation, Nutrition Symposium Serv,, No. 9, 1954. 



