DIGESTION 337 



1. Digestion in Ruminants. 



Prehension. — In the ox, in grazing, the mobile tongue 

 curls round the grass and pulls it into the mouth, when 

 it is cut off by the incisor teeth against the dental pad. 

 The papillae in the inside of the mouth (p. 292) assist in 

 preventing the food from dropping out. The divided upper 

 lip of the sheep allow the teeth and dental pad to bite 

 closer to the ground than in the case of cattle. 



In drinking the lips are closed except for a small orifice 

 which is put below the surface of the water. The tongue 

 acts like the piston of a pump and the water is sucked in. 



Mastication and Insalivation. — Mastication in ruminants is 

 chiefly a side-to-side movement by which the food is ground 

 between the molar teeth. It goes on usually for several 

 minutes in one direction and then changes to the opposite 

 direction. The parotid gland on the side on which the 

 animal is chewing secretes much more actively than that of 

 the opposite side. The sublingual and submaxillary glands 

 secrete equally on both sides. The quantity of saliva poured 

 into the mouth is very large. When dry food is eaten 

 between 50 and 60 litres may be secreted in twenty-four 

 hours. The specific gravity of the saliva is high, nearly 

 1010. 



It is doubtful whether the saliva of ruminants contains 

 any ptyalin. If it is present it is in very small amounts. 



The food is swallowed after a preliminary incomplete 

 chewing. It is returned to the mouth for more complete 

 mastication during rumination which takes place after feed- 

 incf has ceased. Ruminants can therefore eat food about 

 three times as fast as the horse, which completes mastication 

 before swallowing. 



Rumination. — This complication of the digestive process 

 is peculiar to ruminants. It consists essentially of a re- 

 mastication of the food after a preliminary storage. 



(1) Mechanism. — The food, when first swallowed, may enter 

 any of the compartments with which the oesophageal groove 

 is connected fp. 294). Liquids for the most part pass on 

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