64 PHYSIOLOGICAL KEGULATIONS 



It is apparent that an increment of water content {± AW) may 

 be obtained by means that may not ordinarily be thought of as dis- 

 turbing the component water, nor as displacing it in a recognized 

 direction. There is no certain means of foretelling which condi- 

 tions affect water load and which not. Indeed, it becomes probable 

 that there are relatively few states in which the organism can be 

 found that do not involve water loads and water exchanges. It is 

 only arbitrarily and for present purposes that I concentrate atten- 

 tion on increments of water and omit other modifications that 

 accompany them. 



A limited method by which water exchange can be known surely 

 to involve the same type of water load over a period of a few hours 

 is to use a single kind of analysis or measurement for both rate 

 (SW/At) and load (AW), provided water and oxygen alone are 

 available from without. Thus, the weight changes of the dog give 

 both data (exchange and increment) from one difference of weights 

 taken at two times. 



In summary, a few factors may be specified that affect water 

 exchanges under diverse types of water loads. An increment of 

 water {± AW) is not often just a change in water content, even 

 though no other chemical constituent of the organism be known to 

 have changed. 



(1) Time (since ingestion or privation of water) makes a dif- 

 ference in the rates of water exchange. 



(2) Means of addition of water matter. Thus, intravenous in- 

 jection of water was found to produce highly variable results ; the 

 administration being sometimes termed " unphysiological. " 



(3) Means of subtraction of water matter. Thus, the sequelae 

 of catharsis by rectum may not a priori be confused with those of 

 water privation. 



(4) Any accompaniment of addition or subtraction may be of 

 consequence. There probably is no "pure" change of water 

 balance. 



(5) Kation or regime upon which the water load is superim- 

 posed may matter. Thus, whether the alimentary tract is empty 

 or full while recovery is proceeding may be important. 



In general, each type of water load concerns water and a variety 

 of circumstantial factors such as time, locality, responses incidental 

 to introducing or subtracting the water. The bodily system studied 

 is never a homogeneous one, as though a solution were diluted or 



