294 PRINCIPLES OF ANIMAL NUTRITION. 
: A st, 
ro Metabolizable Per Cent 
Cals.’ oe Metabolizable. 
2.905 71.16 
“3.308 79.00 
3.044 : 72.70 
3.176 75.85 
Srarcu.—In a considerable number of the trials commercial 
starch was added to the basal ration. The earlier experiments by 
Kiihn were intended primarily to throw light on the possible for- 
mation of fat from carbohydrates (compare p. 177). In them, 
starch was added to a ration of coarse fodder only and the nutritive 
ratio was purposely made very wide, the result being that more or 
less of the starch escaped digestion. In the later experiments by 
Kellner the starch was added to a mixed ration. Except in the 
first two experiments the nutritive ratio was a medium one and 
but traces of starch escaped digestion. It will be convenient, 
therefore, to tabulate these two classes of experiments separately, 
as has been done in Tables IIT and IV of*the Appendix, the com- 
putations being made as in the previous cases. 
The same remarks which were made on p. 291 concerning the 
distinction between real and apparent metabolizable energy apply 
to these results. As computed they represent the net gain to the 
organism from the consumption of starch and are the algebraic sum 
of several factors. In particular, there was a considerable loss of 
energy in the feces, even in the later experiments in which but 
traces of the starch itself escaped ‘digestion. In other words, the 
starch either lowered the digestibility of the basal ration or in- 
creased the formation of fecal metabolic products or both. The 
method of computation adopted virtually looks upon this as part 
of the necessary expenditure in the digestion of the starch. On 
the other hand, there are severdl cases in which there was a de- 
crease in the outgo of potential energy in the urine, even after the 
results are corrected to nitrogen equilibrium. This, from our pres- 
ent point of view, is credited to the starch and increases its 
apparent metabolizable energy. 
