124 The Feeding of Animals 



Other carbohydrates and related substances, such 

 as the gums and cellulose, do not undergo complete 

 digestion, sometimes half or more of these compounds 

 escaping solution. Stone, after examining twenty feed- 

 ing stuffs and the fecal residues obtained from them in 

 digestion experiments, found in the feeding stuffs from 

 6 to 16 per cent of gums, 46 to 77 per cent of which 

 was digested, the average being 58 per cent. Crude 

 fiber proves to be digestible within about the same 

 limits, or 36 to 80 per cent with American fodders. We 

 are much in the dark concerning the manner of diges- 

 tion of the gums and . crude fiber. To what extent 

 these substances are the subjects of purely fermentative 

 changes, or of merely chemical decompositions, is not 

 known at present, but the fact of a partial digestion is 

 well established whatever may be the causes involved. 



The extent of the digestion and absorption of the 

 fats or oils is also not definitely known. If we were to 

 accept the figures given for ether extract in tables of 

 digestion coefficients as applying to the real fats we 

 would believe that their digestibility varies from less 

 than one -third to the total amount. It is unfortunately 

 true that these coefficients mean but very little. The 

 ether extract from the feeding stuffs is only partially 

 fat or oil, as we have seen, and the inaccuracy of a 

 digestion trial is still further aggravated by the pres- 

 ence in the feces of bile residues and other bodies which 

 are soluble in ether, so that the difference between the 

 ether extract in the ration and that in the feces gives 

 us little information as to what has happened to the 

 actual fats. It seems very probable that pure vegetable 



