38 August Krogh and Marie Krogh. 



X -\- y = Kjeldahl Л" 

 0.908д; + 0.2г/ = Esbach Л^ 



anh we can compute values for x and у from these equations. The 

 figures for urea + ammonia nitrogen and "endogenous" nitrogen 

 given in table 4 have been obtained in this manner. The excretion 

 of "endogenous" nitrogen is found to vary between 2 gr. with a total 

 nitrogen output of 16.4 gr. and 4 gr. with a total output above 50 gr. 



The respiratory exchange. 



Curves representing the respiratory exchange for the two sub- 

 jects taken together and each period of the experiments are shown 

 in figs. 11, 12 and 13 for exp. П, III and IV. For exp. II the CO^ values 

 only are given. Owing to an airbubble of variable size in the absorp- 

 tion pipette for O^ the individual O^ analyses of this experiment be- 

 came unreliable, though the mean for a larger number must deviate 

 very little from the true mean. The oxygen has therefore been cal- 

 culated for 8 hour periods only. 



The curves give very little definite information but show the 

 general character of the variations in metabolism. We find low and 

 fairly constant values for the hours of the night (from 10 to 6). In 

 the day time there are large and irregular variations due partly to 

 the intake of food partly to muscular movements. We had hoped 

 to be able to obtain some information about the movements by let- 

 ting the subjects wear pedometers and reading these at the end of 

 each period, but the results were very unsatisfactory. There appeared 

 to be no relation whatever between the indications of the pedometers 

 and the metabolism found. We are inclined to think that the sub- 

 jects have used the pedometers as convenient playthings. 



The respiratory quotient varies on the whole regularly in accor- 

 dance with the nature of the food taken, being high 0.95 — 0.98 on 

 a carbohydrate diet, and low (about 0.8) on a diet of protein and fat, 

 but sometimes we observe, when the subjects are on this latter diet, 

 a sudden rise of short duration in the quotient. Sudden deviations 

 from the level curve in the opposite direction have not been noticed. 



In order to compare the nitrogen excretion with the corresponding 

 total metabolism we have computed 8 hour values for N^ output, 

 CO2 output and Og intake. We have selected the hours from 10 to 

 6 at night, 6 — 2 in the forenoon and 2 — 10 in the afternoon as corre- 

 sponding as closely as possible with the changes in activity of the 

 subjects and the hours at which the changes in diet should' make 

 themselves felt on the excretions and metabolism. During the hours 

 from 10 — 6 the subjects were in almost all cases asleep or at least 

 lying down, and at 2 in the afternoon the efi'ect of the food taken du- 

 ring the forenoon would generally begin to appear. The results are 



