104 



PHYSIOLOGICAL, EEGULATIONS 



(B, fig. 63). Some single individuals do and some do not show 

 these cycles. One way of testing the significance of the data is to 

 compare the variabilities in rates of output in consecutive hours 

 with those in random hours, in second hours, or in third hours. 

 By any test, the extremes of the cycles appear still to overlap to 

 a probability (P) of 0.05. 



Since the apparent cycles coincided with habitual meal-times, 

 although the subjects of the B tests did not eat, food relations were 



O.20- 



LJ 



o 



Houi^s of +)ie Day 



Fig. 63. Rates of urinary water output (% of BoAour) during steady rates of 

 water intake in relation to clock hours. A, mean outputs in 35 tests on 35 men ingesting 

 every hour 0.11% of B„ of water and 0.13% of Bq of food (actual plus potential water 

 = 0.225%/liour). B, mean outputs in 51 tests on 41 men ingesting every hour 0.11% 

 of Bo of water only. Mean body weights are assumed to have been 68 kg. Means (M) 

 for the 24 or 27 hours and their standard deviations (a) are indicated. At six points 

 on curve A the standard errors are indicated by rectangles. All are data of Gerritzen 

 ('36). 



studied. The day's food was divided into 24 portions and a por- 

 tion was taken with each hour's drinking water (A tests). The 

 cycles were again possibly apparent, in nearly the same positions 

 on the clock. Hence without further change of regime, which in 

 turn would modify additional balances of the body, uniform rates 

 of water exchanges at various hours cannot be expected. This 

 conclusion means that control tests must be made at the same clock 

 times as other tests in any study of water exchanges in man. 



