ELIMINATIOX OF WATER FROM THE HUMAN' BODY 539 



Comment on paper 54 



Shortly after the first application of radioactive isotopes as indicators, in the 

 spring of 1913, the late H. J. G. Moseley and the present writer discussed the 

 prospect opened by the introduction of this method, when indulyinq in a cup 

 of tea at the Manchester Physics Laboratory. The latter then cxpicssed the wish 

 that an indicator might be found which would allow us to determine the fate 

 of the individual water molecules contained in the cup of tea consumed. Even 

 a man of the vision and outlook of the late H. J. G. Moseley considoiod this 

 hope to be a highly Utopian one. It was the discovery of heavy water by Urev, 

 which biought the above-mentioned wish within the range of realization. From 

 the dilution figure of a known volume of administered labelled water, the water 

 content of the organism was evaluated . This was the first application of iso- 

 topic tracers in clinical studies, and the first application of the device of isotope 

 dilution in life sciences [paper 54 and Hevesy and Hofer, (1934) where a more 

 detailed presentation of the results obtained is given]. At present, not heavy 

 water but hyperheavy (tritiated) water is mostly used in such investigations. 

 From the water content of the organism, conclusions can be drawn among others 

 as to its fat content, as shown recently at the Donner Laboratory by Prentice 

 et al. (1951). Assuming the lean body to contain 73 per cent of water, the fat 

 content is calculated according to the formula: per cent body water = 0.73 

 (100 — per cent fat) . 



References 



G. Hevesy and E. Hofer (1934) Klin. Wochenschr. 13, 1524. 

 T. C. Prentice, W. E. Siri, N. I. Berlin, G. M. Hyde, R. J. Parsons, E. F. 

 Joiner and J. H. Lawrence (1952) J. Clin. Inv. 3, 412. 



