68 physiological eegulations 



§ 19. Modifications of water content at balance 



While positive and negative increments of water have been 

 examined, little has been said of states in which water balance pre- 

 vails. These states are both kinetic and stationary. When balance 

 is defined as equality of intake and output, further qualifications 

 are still needed, for in the dog intake is usually intermittent, and 

 output is ordinarily continuous. Moreover, diverse unusual bal- 

 ances can be maintained by repeated ingestions {i.e., in stationary 

 states of load as fig. 24, N), for then within limits the average rate 

 of output equals the rate of intake. 



Hence it is desirable to specify that the term usual water bal- 

 ance applies to those states in which neither intake nor output is 

 forced, where neither privation nor manipulative procedures inter- 

 fere, and where sufficiently long periods (usually 24 hours) elapse, 

 so that rhythms of feeding and sleeping shall be minimized. In 

 particular cases control dogs may be put under more rigidly or less 

 rigidly uniform restrictions of diet, movement, temperature, and 

 the like; it seems quite impossible to define water balance with 

 great generality and yet with rigor. 



Often a steady balanced state is approached, when the environ- 

 ment or the body is changed, that differs from the state that would 

 be recovered in the original environment or organic state. The 

 modifications of water content and the rates of these shifts (total, 

 net; gain, loss) may sometimes be measured also during the trans- 

 ition. 



I know of no data that compare accurately an equilibration of 

 Wo that has been shifted by a known content with an unshifted 

 equilibration diagram in the dog. What is here discussed are, 

 therefore, consequences of partial data as generalized in the light 

 of relationships so far outlined. 



Some instances of modified turnovers are as follows. If dogs 

 are deprived of anatomical connections between hypophysis and 

 brain, the intake and the output of water (turnover) increase 

 enormously and in two cycles (Bellows and Van Wagenen, '38). 

 Administration of desoxycorticosterone induces persistently high 

 turnover (Ragan et al., '40). Surgical imposition of Eck fistula 

 increases the exchanges of water (fig. 41), with gradual recovery 

 toward usual rates. Chloroform-poisoning gives a smaller in- 

 crease of turnover; but ligation of bile-duct and certain other 

 surgical procedures do not. Where on the scale of water contents 



