Discussion 115 



Dr. Maclntyre of Hammersmith has made an interesting study (to be 

 published), in which he finds a direct correlation between either body 

 weight or body fat and the extracellular space as measured by bromide. 

 The implication of this correlation is that fat tissue has an extracellular 

 space relationship to its weight which is the same as that of non-fat 

 tissue. This relationship is consistent with the data presented by Dr. 

 Olesen. 



Bull: This is in contradistinction, for instance, to the blood volume, 

 which is a poor function of total body weight or of fat, and is closely 

 related to lean body mass. I would suggest that blood volume and meta- 

 bolic rate are related to intracellular water and possibly to exchangeable 

 potassium rather than to extracellular water. 



McCance: Do those who see many old people professionally get the 

 impression that they are fatter than middle-aged people? There are 

 often indications that in old age man is rather wasted and has not much 

 fat ; but perhaps his shrinkage is more in protoplasm than in fat. 



Swyer: One possible interpretation is that fat people do not live so 

 long; most of the really old people are pretty thin. 



Fejfar: My experience is that older people usually eat more than they 

 did when they were middle-aged — they eat more than they need to. 



Shock : I have no information on what they eat, shall I say, spontan- 

 eously. But I do know that on many metabolic balance studies that we 

 carried out on middle-aged and older people, one of our primary prob- 

 lems was to get our older people to consume the diets which were eaten 

 by the middle-aged control group without much difficulty. The varia- 

 tions were usually in the protein intake, particularly when we tried to 

 increase it by adding meat three times a day. A great deal of coaxing was 

 needed to get our older people to consume diets of this kind. 



Fourman: Dr. Olesen, Dr. Shock and others suggest from their data 

 that, in adults, the percentage of total body water that is extracellular 

 water increases with age. I would like to try to visualize what this means. 

 One should not think of the extracellular fluid as a bag of water. Ob- 

 viously about a quarter of it is accounted for by the plasma volume, and 

 perhaps a fifth by the lymphatic fluid ; but what about the rest? The rest 

 is a film of fluid which surrounds the cells and the fluid of the collagenous 

 tissue of the body. If the cells, the muscle cells in particular, without 

 changing in number, shrink with age, then one would get a change in the 

 relation between the volume of the muscle cells and the amount of fluid 

 bathing them, since a single cell when it shrinks increases its ratio of 

 surface area to volume. I wonder whether this is the explanation of the 

 increase in ratio of extracellular to intracellular water with age : a shrink- 

 age in each cell without change in the total number of the cells, but each 

 cell still having to have its film of fluid surrounding it. 



