268 



PHYSIOLOGICAL REGULATIONS 



Equilibration diagrams, then, change as the pup develops (fig. 

 137). At birth, turnover of water (per unit of body weight) is 

 double the adult's, and in water loads the modifications in rates of 

 exchange are small. With surprising suddenness, rates both of 

 gain in deficit and of loss in excess attain high velocity quotients. 

 Only upon a few days of the pup 's life can intermediate stages be 

 found. Thereafter, the time required for recovery from water 

 load is independent of body size. Turnover, however, slowly di- 

 minishes (as the ratio of surface to mass decreases). The tran- 

 sition to compensatory processes makes clear how inadequate is the 

 provision for adjustments in the newborn pup; and, by contrast, 



Loss 



+2 



Total Water Load 



+4 



+6 



Fig. 137. Eate of total water exchange (% of Bo/hour) in relation to administered 

 water load (% of Bo). Equilibration diagrams. Young dogs in the first 1.0 hour of 

 recovery. In excesses, pups up to 15 days of age had their bladders emptied by punc- 

 ture through the body wall; at later ages micturition was spontaneous. Solid points 

 represent newborns at 1 to 5 days of age, crosses those 7 to 15 days of age, and open 

 points those at 16 to 32 days of age. New data. Adult dogs may be compared from 

 figure 13. 



emphasizes what the pattern of equilibration enjoyed by the adult 

 accomplishes. 



In man within the first days of life the rate of water turnover 

 increases daily (Drossel, '29). The rate of urinary water output 

 progresses from 0.02% of Bo/hour in the first day, to 0.24% of 

 Bo/hour in the sixth day (Gundobin, '21, p. 363). Of course this 

 change is related to the interruption of nutrition at the metamor- 

 phosis of birth, and the gradual increase in intake of food (and 

 water) during the first week. Throughout the first year the rate 

 of urinary output subsequently diminishes in relation to body 

 weight, being nearly proportional to B°'^, when judged from Gun- 

 dobin 's data. 



