IO2 STORRS AGRICULTURAL EXPERIMENT STATION. * 
to 500 grams for six hours, the simple return to rest was fol- 
lowed almost immediately by a return to the normal elimina- 
tion orCOs. : 
In the case of the elimination of nitrogen in the urine, 
however, the increase consequent upon hard muscular work, or 
the decrease when the body was in a state of rest, did not mani- 
fest itself until some hours after the muscular work began or 
ended. This interval, during which the excretion of nitrogen 
lags behind the metabolism, and which we have got in the way 
of calling the ‘‘ nitrogen lag,’’ may be assumed to be longer or 
shorter. For instance, it may be supposed that the nitrogen 
metabolized in a given day beginning at six in the morning 
will be excreted in the urine of the day beginning the follow- 
ing noon, thus allowing a lag of six hours. ‘This assumption 
was actually made in the calculations of nitrogen balance in 
one of the experiments here reported. In another experiment 
a lag of twelve hours was allowed for. As explained in the 
discussion of the details of respiration experiment No. 4 be- 
yond, thirty hours may be a more nearly correct period, and 
estimates are made accordingly. 
We have been unable to find data for judging at all accu- 
rately as to the length of this interval of lag. For that mat- 
ter it is doubtless impossible to make any accurate estimate, 
for there is no assurance that either exactly the same nitrogen 
or the same amount of nitrogen that is metabolized during a 
given period will be contained in the urine of any other period 
of equal length unless both periods are very long. Sufficient 
evidence of this is found in the fluctuations in the daily nitro- 
gen excretion in the experiments herewith reported, when the 
diet and other conditions were reasonably uniform. 
RESULTS OF THE RESPIRATION EXPERIMENTS. 
The detailed results of these experiments are given in the 
Bulletin of the Department of Agriculture above referred to, 
in which the methods of calculating the results from the numer- 
ous data are more or less fully explained. It will, therefore, 
suffice here to briefly recapitulate the principal data. Those 
for ventilation and CO, exhalation are epitomized in table 9 
beyond. Those for nitrogen and carbon balance are summar- 
ized in tables 7 and 8 herewith. 

