DIGESTIBILITY OF FISH AND POULTRY. L255". 
In Table 13 the amounts of the various foods eaten during 
the experiments are given, together with the weights of the 
partially dried feces and of the urine of the third day. The 
weights of fresh feces are not given since the analyses were 
made on the partially dried samples, and the computations 
of nutrients may be made from these data, irrespective of the 
total water content. 
CALCULATION OF RESULTS. 
The details of the separate digestion experiments are given 
in Tables 14 to 17 beyond. The kind and amounts of food eaten 
are first given as shown by Table 13. These amounts multiplied 
by their respective percentage composition and heats of com- 
bustion (taken from Table 12) give the weight of nutrients and 
energy in the total diet. In the same way the amounts of 
nutrients and energy in the partially dried feces are also 
computed. 
Availability of nutrients of the total food.—The difference be- 
tween the quantities of each nutrient in the total food and the 
amount of the corresponding nutrient in the feces is assumed 
to represent the amount digested. Dividing the amount di- 
gested by the corresponding amount eaten and multiplying by 
100 give the proportion digested on a percentage basis, or as it 
is generally called, the coefficient of digestibility. 
Strictly speaking, the results thus obtained do not represent 
actual or true digestibility, for the reason that the feces contain 
not only the portions of food that happen to escape digestion, 
but also other materials, such as the residues of digestive juices, 
bacteria, and intestinal debris, which collectively comprise what 
are commonly designated as metabolic products. To determine 
true digestibility it would be necessary to separate these meta- 
bolic products from the actually digested food, and deduct the 
ingredients of the latter from those of the food eaten. Thus 
far, however, no satisfactory method for separating the differ- 
ent constituents of the feces has been devised; consequently 
the actual digestibility of the food is not easily determined. 
On the other hand, since the real object of digestion experi- 
ments such as are here reported is to determine what proportion 
of the food and its several ingredients is actually made avail- 
able to the body for the purposes of nutrition, the metabolic 
