690 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 
that the relative constancy of the nitrogen excretion in the urine under 
very marked change in intake is one of the surprising features of the 
research. 
The comparison between the nitrogen of the food and the nitrogen 
in urine leads, of course, to the consideration of the large nitrogen 
losses. These are so significant and of such magnitude that we have 
deemed it advisable to plot them in the form of a curve showing the 
accumulative nitrogen loss, which is a curve that continues downward 
as the experiment progresses. This appears near the lower part of 
the chart and shows a final loss at the end of the experiment of not 
far from 175 grams of nitrogen for the average of 9 men. Sufficient 
attention has been called in the earlier text to the difficulties of accurately 
estimating the total nitrogen loss, owing to the uncontrolled days, on 
the one hand, and to the loss through the skin and perspiration on the 
other. 
One of the most important physiological measurements showing 
general condition is the blood pressure, which is frequently reported 
with these men. The average blood-pressure curves show systolic, 
diastolic, and pulse pressure. All three curves have much the same 
trend, namely, a distinct falling off up to November 25, with a ten- 
dency for minimum values appearing shortly thereafter, then a slight 
rise in systolic and diastolic pressure to January 12, after which, 
although the systolic and diastolic pressure curves are parallel, the 
pulse pressure is in the opposite direction. Pronounced reductions of 
all three factors are worthy of special emphasis. 
Pulse-rates were recorded frequently throughout the entire series 
under several conditions. The normal pulse-rate was observed with 
the subject lying in the morning in the post-absorptive condition. (See 
lower part of figure 124.) The curve shows a distinct tendency towards 
a fall in the first part of the experiment, a plateau at the low level in 
November, a sharp fall from a higher level following the Christmas 
recess, and a slight rise toward the end of the experiment. 
The important relationship between the pulse-rate and muscular 
work is indicated by the records computed from Professor Johnson's 
data, with the subject lying 1 minute before work, 1 minute after work, 
and the percentage increase 1 minute after work. The pulse-rate 1 
minute before work, although at a distinctly higher level, is obviously 
more or less comparable with the pulse-rate obtained in the morning 
with the subject in the post-absorptive condition. The form of the two 
curves is not unlike, the pulse-rate 1 minute before work showing a de- 
crease in the early part of the experiment, followed by a pronounced 
rise, with a striking increase immediately after the diet restriction 
ceased. This great increase was followed by a distinct drop following 
more normal eating. 
