Body Water Compartments throughout Lifespan 103 



sulphate is smaller than the corrected volume of dilution of 

 radiobromide the values for extracellular volumes will not be 

 directly comparable for the children and the adults. The same 

 will apply to the calculated intracellular water. All the 

 methods used are reproducible within the 5 per cent range. 

 As the absolute quantities measured are difficult to compare 

 from one individual to another it has become customary to 

 express the results as relative values. The standard of refer- 

 ence used is the body weight as this standard in our experience 

 has been the most simple. In the interpretation it is important 

 to realize that a rather large biological variation appears 

 within groups of the same age and sex. 



Although the study of the body water compartments 

 throughout the lifespan is still fragmentary, certain trends 

 in relation to age and sex have appeared. It will be the 

 purpose of this paper to outline these features in a description 

 of the body water compartments during the three main phases 

 of life : growth, maturity and ageing. 



Growth 



Growth implies a variety of fundamental processes: cell 

 multiplication, increase in cell size, accumulation of extracel- 

 lular material, increase in fat and minerals. 



The alterations in the body water compartments during 

 growth have been studied by Friis-Hansen (1956). From a 

 series of 93 normal children studied with deuterium oxide, 

 with thiosulphate or with both, a series of 31 individuals with 

 simultaneous measurements of all three water compartments 

 will be presented. 



It appears from Table I that the absolute amounts of total 

 body water, of extracellular water, and of intracellular 

 water demonstrate an increase throughout infancy and child- 

 hood. It is seen that the intracellular water rises more 

 markedly than the extracellular water. 



In Table II the three measurements are given as percentages 

 of body weight. The total body water shows a relative de- 

 crease throughout infancy and childhood with a most marked 



