180 STORRS AGRICULTURAL EXPERIMENT STATION. 
the probability that these materials, taken by themselves, are 
not digested as completely as when they form a part of a mixed 
diet. | 
With reference to the figures of table 53; it should be observed 
that the results are subject to the errors inherent in experiments 
made by the current methods as above stated. ‘The principal 
sources of error are probably three: (a) defects in the ordinary 
methods of analysis; (4) failure to make allowance for metabolic 
products, which are here considered as belonging to the undi- 
gested residue of the food, though they actualiy represent 
material which has been digested; (c) variations due to individ- 
uality of the subject and other influences not well understood. 
The error due to imperfections of analysis, while important, is 
probably not large. The error from treating the metabolic 
products in the feces as if they were a part of the undigested 
residue of the food, is small and of theoretical rather than 
practical interest,so far as concerns the nutriment actually 
obtained from the food. ‘The variations in digestion of the 
same food by different persons may be more or less consider- 
able. As regards the variations of digestion of food by the 
samine person under different conditions, the results of inquiry 
up to the present time lead to the inference that while the 
digestive apparatus of the subject is in normal condition, and 
the quantities of food are also normal, the coefficients of digest- 
ibility are much less affected by exercise or rest than is com- 
monly supposed. ‘There does seem to be ground, however, for 
the belief that in ordinary mixed diet the digestion is gen- 
erally more complete than where only a single food material 
is eaten. 

