102 General Discussion 



The measurement, for example, of renal function alone and correlating 

 it to age alone cannot avoid the error of not including pathological 

 conditions in a group whose only object is to investigate age changes. 

 A diminished cardiac output can be the result, in an ageing person, of 

 a disease leading also to a diminished blood supply to the kidney and 

 reduced renal function. This confusion is very frequent in geronto- 

 logical research, especially with a "physiological" reduction of func- 

 tion as correlated to age alone. From this I draw the conclusion that 

 single measurements or even multiple measurements not carried out 

 simultaneously are valueless. 



Friedman: I find myself in agreement with Dr. Olbrich insofar as 

 the rat data which we have support his contention for man. I am 

 not sure how far one can go to establish primacies on this sort of 

 thing, but certainly what he says about relating measurements to 

 one constant measure is an extremely good point. 



I would point out that that shift in body water has been mentioned 

 in the past ; Lowry and Hastings have dwelt on it fairly extensively 

 (Lowry, O. H., and Hastings, A. B. (1952). In Cowdry's Problems 

 of Ageing, 3rd edition. Ed. A. I. Lansing. Baltimore: Williams & 

 Wilkins). The point about relationships of metabolism in general to 

 fat-free body mass has been driven home fairly often and perhaps 

 not enough attention has been paid to it. 



Olbrich: Hastings measured extracellular water with sodium thio- 

 cyanate which did not, in fact, measure the extracellular space, as 

 this substance penetrates the cells. The penetration takes place at 

 different rates in different age groups, so his values for extracellular 

 water were surprisingly high and the variation in his extracellular 

 water measurements was considerable. 



When total body water is measured with antipyrine or NAAP 

 (A^-acetylaminoantipyrine) and the results are plotted and extra- 

 polated to zero time, there is also great variation. Five members of 

 my staff independently plotted the obtained antipyrine values and 

 extrapolated them, and their results varied greatly. Prof. McCance 

 suggested using urea, as urea penetrates all the cells, and I find the 

 urea method gives fairly constant measurements. We know the error 

 and we know the extent of the error. 



For measurement of the extracellular water we are using either 

 inulin or sodium thiosulphate. It is only when the same experimental 

 methods are applied in both humans and animals that corresponding 

 values can be obtained and only then will data on humans and on 

 animals correspond. 



Best: Perhaps Prof. Nicolaysen would say something about how 

 we are going to proceed in the investigation of nutrition in relation 

 to ageing, and whether or not animal results can be applied in the 



