286 PHYSIOLOGICAL REGULATIONS 



of diverse processes, behaviors, and others. Ascertain their 

 deviations. 



(6) Set down the quantitative changes that are measured and 

 their interrelations, remembering that water content is the quantity 

 whose maintenance is to be examined. 



(7) Note the unique and the general characteristics of each 

 system (group of variables) described. 



(8) If desired, find whether some of the changes vary progres- 

 sively with repeated imposition of the same water increment (ac- 

 climatization, facilitation). 



There is nothing very peculiar about this procedure ; it is a par- 

 ticularized and explicit form of any plan of experiment. It em- 

 phasizes the fact that materials and conditions are selected, the 

 precision of time and of quantities, and the notion that what the 

 experimenter does is much the same, regardless of the hypotheses 

 that he entertains. In a primitive stage of physiology, an investi- 

 gator of water relations might stop with stage (3) or (4) or (5), 

 and might be content with a qualitative answer to a single question. 

 At present, the most complete quantitative description is required 

 to answer any comprehensive question concerning water relations, 

 forming a durable part of a maturer science of physiology. In the 

 future, still further steps may be added. 



<§s 105. Outline of water relations 



Using the specific materials in earlier chapters, I can now sketch 

 the investigation of water maintenance and its correlatives without 

 the details. This recapitulation in general terms allows emphasis 

 on uniformities found among many instances, and disregard of 

 elements that vary with species or parts, and with conditions. 



At the outset, ivater increment or load was defined as the differ- 

 ence of water content in the organism or part in two physiological 

 states, namely, test and control. In general, control states were 

 arbitrarily chosen, but a further definition of them was found in 

 the existence of water balance (equality of intake and output rates) 

 in what are believed to be standard, usual, resting, or occasionally 

 basal, situations. Sometimes the biologist has difficulty in choos- 

 ing ''natural" conditions for an organism or its isolated parts, but 

 he can usually define the conditions existing. 



With water increment were correlated diverse variables that 

 had been measured simultaneously or in other relation with it. Of 



