IMPERIAL COLLEGE OF 
6 
deducting always the nitrogenous matters and ash from the 
raw fibre found. The ash was estimated after incineration 
and determination of the carbon and carbon dioxide con¬ 
tained therein, which were deducted from the raw ash. 
For the sake of simplicity, we use, in the following pages, 
the terms of “fat,” “fibre,” “ash,” instead of always 
repeating, “ crude fat,” “crude fibre, free from nitrogenous 
substances and ash ” and “ pure ash, free from C and C0 2 .” 
In the calculation of the digestibility the contents of 
the fæces were simply taken as undigested food ingre¬ 
dients, although it is known that they are mixed with some 
digestive and other juices, mucin, epithelial cells, etc., 
which I have shown to be considerable enough to alter 
materially the numbers for the digestible crude protein. 
We did not beforehand take account of those facts, because 
the feeding standards as well as the tables on the digestibi¬ 
lity of feeding stuffs have also been compiled without 
knowing them. Besides this the nitrogen admixed with 
the fæces in the digestive canal is approximately depend¬ 
ent upon the total dry matter digested, as I have formerly 
found. The figures calculated in the present paper might 
consequently be easily corrected, if any necessity would 
arise in future. 
