equdijIbrations in parts of organisms 



159 



numbers of studies that have been reported upon the volumes of 

 such organs, none indicates the rates of recovery of volume after 

 diverse amounts of fluid have accumulated in them or been lost 

 from them. Most of the changes measured are probably in amounts 

 of intravascular blood contained in these organs ; suitable pressure 

 plethysmographs remain to be applied to livers, kidneys, and 

 muscles. 



Changes of volume as inferred from measured changes of con- 

 centration in analyzed samples of these organs, would be significant 

 6 



+2 



Water Load 



Fig. 97. Eate of volume output (% of control arm volume /hour) in relation to 

 initial volume load (% of Vo) in the human arm. The load has been imposed by previ- 

 ous venous congestion, and the subsequent changes in "reduced" arm volume are as- 

 certained in initial periods of 0.17 hour in a plethysmograph at 34° C. Data of Landis 

 and Gibbon ('33). 



only if the changes are larger than the standard errors among 

 samples. Those are usually very large. But occasionally the con- 

 centration may be measured optically upon one portion of tissue 

 in situ. By that device control data are ascertained on the same 

 sample, avoiding errors of absolute factors and of variabilities 

 among samples. Further advantages are found in studying recov- 

 eries from those increments of volume that are predominantly in the 

 tissue in question rather than in the remainder of the body; such 

 was actually the case for blood, plasma, and arm. 



