252 PHYSIOLOGICAL, REGULATIONS 



total water exchanges, total contents of diverse substances, rates 

 of various total metabolisms, and some behaviors are available. In 

 large animals and man, total contents have not been analyzed in 

 diverse ± AW. Metabolisms also are very likely to be studied by 

 methods not strictly comparable in diverse species. The actual 

 data cover only two sorts of measurements in several species : dilu- 

 tions of dry residue in particular organs, and rates of oxygen con- 

 sumption. 



With respect to rates of oxygen consumption, the only apparent 

 uniformity is that found by Caldwell ('25, '31), in animals sub- 

 jected to progressive evaporation and privation of water ; namely 

 that oxygen is consumed in moderate deficits of water slightly more 

 rapidly than in controls, and in more extreme deficits equally or 

 less rapidly than in controls. The definition of "moderate" and 

 ''extreme" is numerically diverse in the several species, and even 

 so, exceptions have already been found. It is not implied that the 

 increased rate of oxygen consumption is independent of increased 

 muscular movements, nor that the movements are or are not 

 * ' voluntary. ' ' 



In comparisons among existing data, some interpolation is 

 required to relate the data to some common increment of water 

 content. An experimental increment of water that seems heroic 

 for man appears to investigators so small as to be hardly worth 

 studying in frog or worm. Of course, anyone is free to decide that 

 body weight is not the most desirable basis for computing incre- 

 ments ; but objections attach to any other possible basis, I believe. 



Apparently the leading motive in the study of changes in blood 

 after forced water ingestion was the picture that a modified blood 

 circulating through the kidneys may excite them to specific activi- 

 ties. Extended investigation in man suggested that "the elabora- 

 tion of urine is not or at least not solely dictated by the condition 

 of the blood" (Farkas, '32). Part of the lack of parallelism be- 

 tween blood and excretion is that demonstrable blood dilution pre- 

 cedes the increase in rate of urinary output (Rioch, '27). Dis- 

 covering this, some investigators relinquish this picture and the 

 studies it suggests, while others modify the picture to suit the facts, 

 as is readily done. Other notions initiated other studies. The 

 supposition that the organism spends energy to eliminate the excess 

 water, led to measurements of oxygen consumption in body (and in 

 kidneys) ; the theory that the kidneys were informed of water 



