298 PHYSIOLOGICAL REGULATIONS 



description) were selected. Then data concerning water incre- 

 ments and exchanges in the dog were studied intensively, and 

 particular correlations between them were specified. After like 

 data in other species were added, comparisons among them were 

 drawn, together with a number of generalizations. Further, it be- 

 came evident that parts of organisms, even single cells, could be 

 treated in the same manner as whole individuals ; for each unit pre- 

 served and recovered volume. The variable labelled water incre- 

 ment was kept throughout, while diverse changes of compositions, 

 metabolisms, and other physiological activities were correlated with 

 it. Finally some general properties of organisms having increments 

 of water or volume were enumerated and quantitatively compared. 



It might be asked: why was the maintenance of water in the 

 whole body studied, instead of maintenance of water in the blood 

 plasma, whose role as the ''internal medium" of the organism has 

 been emphasized since Bernard (1859, p. 42) first pointed it out? 

 I think it is clear that exchanges by gains and losses, behaviors 

 toward environments, successive variabilities of content, and 

 correlated events, are capable of much more complete and accurate 

 study on the body as a whole. For, water could be measured as it 

 went in and out, it and other metabolites could be located, sensory 

 phenomena could be studied, and fluctuations from hour to hour 

 could be evaluated for the whole; whereas for the plasma alone 

 little quantitative accuracy has been achieved and few exchanges 

 are known. These are the advantages that carried the investiga- 

 tion of water regulation beyond the stage at which Bernard left it. 



Many more properties of water-loaded organisms will come to 

 light when further observations are added, for no one investigation 

 is likely to exhaust the possible interrelations. The pattern of 

 interrelated quantities that has been ascertained serves provision- 

 ally to describe the regulation of water content in the organisms 

 studied. Once it is known what features are characteristic when 

 water content is regulated, it becomes worthwhile to see whether 

 other components of organisms are regulated in similar ways. 



