73 
It thus appears from the table that the feces from the digestion 
experiments made with fruitarians here reported are not excessive in 
amount, as has usually been found to be the case with experiments 
with a vegetarian diet containing very little or no fruit. 
METABOLIC NITROGEN IN THE FECES. 
When considering the digestibility of any article of food it is quite 
important that allowance be made for the so-called metabolic prod- 
ucts/' At present there is no accurate method in vogue for the 
separation of the metabolic nitrogen from the nitrogen belonging to 
the undigested residue of the food in question, which is necessary 
in determining the true or absolute digestibility. The coefficients of 
digestibility of protein, therefore, which are obtained without taking 
into account the metabolic nitrogen, are lower more or less than they 
should be. 
If, however, the digestibility of any food or combination of foods 
is looked at in another light, the matter appears somewhat differently. 
Whether a certain amount of nitrogen is lost to the body through the 
undigested residue of the food, or whether it is lost through the 
metabolic products, makes practically no difference as regards the net 
income of nitrogen from the food; or. in other words, the real value of 
that food or food combination as a source of nitrogen to be utilized for 
other functions of the body than digestion. 
The metabolic nitrogen in the feces in nineteen of the experiments 
was determined, the method followed being the same as that previously 
used;* that is. the feces were treated successively with hot ether, hot 
alcohol, hot water, and cold limewater, reagents which experiment 
has shown dissolve the metabolic products present. 
The results of these analyses are given in Table 55. 
Table 55. — Total nitrogen infers* and nitrogen corrected for metabolic product*. 
Ex- 
peri- 
ment 
No. 
Kind of food. 
Dura- 
tion of 
test. 
Amount 
of feces 
i water- 
free). 
Nitrogen — 
In un- 
treated 
feces. 
In feces 
treated 
with re- 
agents. 
In meta- 
bolic prod- 
ucts. 
391 
SUBJECT C. P. H. 
Bananas 1st day 
Days. 
Gravis. 
20. 30 
17.60 
19. -50 
Per cent. 
4.61 
4.15 
4.40 
Pt r cent. 
3.20 
3.65 
3.69 
Per cent. 
1.41 
Bananas, 2d day 
.50 
Bananas, 3d day 
.71 
For whole period 
Bananas and almonds, 1st day 
3 
57. 40 
4.41 
3.50 
.91 
392 
54. 00 
2.79 
30.00 
85. 24 
4.72 
4.94 
4.42 
3.99 
3.30 
3.59 
3.52 
3.29 
1.42 
Bananas and almonds, 2d day 
1.35 
90 
Bananas and almonds, 4th day 
.70 
For whole period 
4 
172.03 
4.31 
3.34 
97 
"See discussion of the subject in U. 8. Dept. Agr.. Office of Experiment Stations 
Buls. 85 and 107. 
6 U. S. Dept. of Agr., Office of Experiment Stations Bui. 107. 
