DIGESTION 341 



The stomach contents for some time after being received 

 from the omasum are alkaline. Micro-organisms flourish and 

 break down sugars to form hictic acid. An amoh'tic enzyme 

 converting starch to sugar seems to be produced. 



Before this amolytic period is completed pepsin and 

 hydrochloric acid are secreted in sufficient amounts to make 

 the contents acid and enable peptic digestion to begin. The 

 concentration of hydrochloric acid, however, is never so great 

 as in carnivora. 



Intestines. — In the small intestine, so far as is known, the 

 secretions and digestive processes are the same as have been 

 described for carnivora. But a smaller proportion of the 

 food is digested and absorbed so that a bulky residue reaches 

 the ciBcum and colon. Here the destructive fermentation of 

 cellulose by bacteria is resumed, and digestive processes are 

 continued by enzymes that have been carried on from the 

 small intestine. The large intestine is therefore a more 

 important structure in herbivora than in carnivora, where its 

 main function is the absorption of water and the storage of 

 food residues and excretory products prior to expulsion in 

 the faeces. 



In ruminants where important changes go on in the 

 rumen before the food passes through the stomach and small 

 intestine disrestion in the caecum and colon are much less 

 important than in the horse (p. 344). 



Faeces. — The fseces which consist chiefly of undigested 

 residues of the food are more fluid in the ox than in the 

 sheep. The amount varies with the food. In the ox the 

 average weight per diem is about 30 kilos. The composition 

 of the fgeces is dealt with later (p. 861). 



2. Digestion in the Horse. 



Prehension. — In grazing, the lips of the horse are drawn 

 back to allow the teeth free access to the grass. If the 

 nerves supplying the lips cut, it becomes impossible for the 

 horse to graze. In manger- feeding the lips are used to 

 gather the food. 



In drinking, as in the ruminant (p. 3 37), the tongue acts like 



