go NUTRITION OF FARM ANIMALS 



amounts of cellulose-dissolving enzyms (cytases) found in some 

 feeds appear quite inadequate to account for its solution, so 

 that the manner of its digestion was long a puzzle. The in- 

 vestigations of Wildt l in 1874 upon the digestive process in 

 sheep, however, showed, as Zuntz 2 subsequently pointed out, 

 that the solution of cellulose occurs chiefly in those portions of 

 the alimentary canal where the feed stagnates, that is, in 

 the paunch of the ruminant and in the ccecum and colon. 

 This fact tended to confirm the view already advanced that the 

 solution of cellulose in the digestive tract was due to a process of 

 fermentation, and this hypothesis also served to explain the 

 presence of methane and hydrogen in the digestive tract. Tap- 

 peiner, 3 however, seems to have been the first to show ex- 

 perimentally that the disappearance of cellulose in the digestive 

 tract is effected by a fermentation brought 'about by the micro- 

 organisms inhabiting the alimentary canal. 



Tappeiner's conclusions have been fully confirmed by more 

 recent investigations, notably those of Markoff 4 in Zuntz's 

 laboratory, while Kellner 5 has shown that the consumption of 

 crude fiber (straw pulp) by cattle causes a marked increase in 

 the amount of methane eliminated. In the light of these 

 results it may be regarded as established that the disappearance 

 of cellulose during its passage through the alimentary canal of 

 herbivora is not due to a digestion in the sense of a simple hydro- 

 lytic cleavage, like that of starch or protein, but to a destructive 

 fermentation. The products of this fermentation are large quan- 

 tities of carbon dioxid and methane and small amounts of hydro- 

 gen, which are excreted, and various organic acids of the aliphatic 

 series which combine with the alkalies of the saliva or other 

 digestive fluids. The salts thus formed are resorbed and consti- 

 tute the sole contribution which cellulose makes to the nutrition of 

 the body. The principal acids formed appear to be acetic and 

 butyric, although others are also . present. In ruminants, the 

 chief seat of this fermentation is the capacious first stomach, 

 while in the horse, with his relatively small, simple stomach, 

 it takes place principally or wholly in the enormous ccecum and 

 colon. 



1 Jour. Landw., 22 (1874), i. 2 Landw. Jahrb., 8 (1879), 101. 



3 Ztschr. Biol., 20 (1884), 52. 



4 Biochem. Ztschr., 34 (IQII), 211 ; 57 (1913), i. 



5 Landw. Vers. Stat., 53 (1900), 193, 300. 



