304 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 
18, inclusive, when the subjects had approximately a maintenance 
ration, at least so far as caloric intake was concerned, is shown in 
table 43. The average nitrogen excretion for the entire 12 days was 
10.92 grams per man per day. The variations in daily averages are 
somewhat larger than in the earlier part of the experiment, for here 
they range from 9.80 grams on December 14 to a maximum of 
12.21 grams 3 days later, but are reasonably uniform, the average 
value, 10.92 grams, being a little over 1 gram less than the average 
value found for the first 12 days of the research. In other words, we 
see clearly that we deal with no large variations in the daily excretion 
of nitrogen, considering the squad as a whole. 
The average nitrogen intake in the food from October 1 to 10 in- 
clusive (table 40) was 12.71 grams, although on 3 days high values were 
observed. The average of the first 3 days is 15.47 grams; the average 
of the last 7 days is 11.53 grams. The irregularity of the intake of 
nitrogen, even after the curtailment in the diet began, is shown by 
the fact that on October 7 the average nitrogen intake was 9.33 grams 
and on the next day it was 4.5 grams larger. Notwithstanding these 
relatively large variations in the nitrogen intake, the average urinary 
nitrogen (table 41) remained singularly constant throughout this period. 
The nitrogen in the food intake in the period from December 5 to 
18 is shown in table 42. Considerable variation is also found in these 
amounts, the daily averages ranging from the low value of 8 grams 
on December 7 to a maximum of 13.52 grams on December 17. 
The minimum average of 8 grams is 3 grams lower than the general 
average of 10.99 grams, and the maximum average is 2.5 grams higher. 
Turning again to the urinary output during this period (table 43), 
it is perhaps surprising that we find a greater degree of uniformity 
obtaining, for while there are variations, they do not approximate in 
size the variations found in the food intake. The fact that the average 
nitrogen intake in the period of December 5 to December 18 is 10.99 
grams and the average nitrogen output in the urine is 10.92 grams 
shows that these men were not in nitrogen equilibrium, for no allow- 
ance has been made for fecal nitrogen or for losses through the skin. 
So while these subjects were in weight equilibrium, they were not as 
yet in nitrogen equilibrium. Mention is made of this here to emphasize 
the fact that while nitrogen equilibrium may suggest weight equilib- 
rium, the reverse is by no means true. (See page 353.) 
The inspection of the fragmentary evidence of the nitrogen intake 
and output, as shown in these sections of the food and urine tables 
for the two periods of the experiment, makes it necessary to present 
in abstract form the average nitrogen in the food and urine per man 
per day for the entire experimental period, for the relationship between 
them is an important one. Tables 40 to 43, inclusive, give not only the 
average values, but likewise the values for each man, and permit a study 
