OTHER TYPES OF WATER INCREMENT 65 



concentrated with prompt mixing; but a highly diversified one, 

 such that only one type of carefully specified procedure may give 

 a set of reproducible results. What at first appears to be an incre- 

 ment of a single chemical entity is in reality an arbitrarily chosen 

 complex; indeed, no increment without a "complex" seems physi- 

 ologically possible. 



The term "hydration," like "dehydration" and many other 

 terms that might be cited, may have been first used (in connection 

 with animals) to designate a particular change in the organism. 

 Later supposedly similar changes were assigned the same name. 

 The early attempt to group like states has now probably passed its 

 usefulness, and a need prevails to separate these states according 

 to their dissimilarities. A dozen types of water excess are here 

 compared (table 3), and at least thirty more have been experimen- 

 tally observed in part. Additional procedures and responses may 

 at any time be distinguished and the present types be subdivided 

 accordingly. 



Finally, I recognize that many investigators are more inter- 

 ested in what goes on within the dog than in the overall responses 

 to water load. How does the body recognize the presence of load? 

 What tissues are excited, what ones transmit messages in accord- 

 ance with the load present ? Implicit in the fact that exchanges are 

 correlated with load and with one another, is the existence of co- 

 ordination and its machinery. To small degrees their locations 

 may be made out by methods of isolation and interference, making 

 use of physical, chemical, pathological, and surgical procedures of 

 various sorts. All those tools are also, however, specifications of 

 the diverse types of water load; they are conditions of recovery. 

 Here the emphasis is not upon the parts played by each anatomical 

 or chemical bit of the organism ; yet the same facts are included in 

 the account exhibited above. Those facts seem to me to furnish 

 help in the study of regulations in this one respect, namely, how 

 differently do dogs get along when their compensations are 

 abolished? If all are abolished for long, dogs do not survive. 

 But over limited periods of time each path of exchange, each means 

 of communication and distribution, and each excitable tissue may 

 be out of commission. 



Specific physiological factors for recovery of water balance in 

 the dog are far from intimately known. For polyuria to follow, 

 water may be administered by many routes; the most prompt 



