MASTICATION. 



79 



of the teeth. Hence, mastication becomes less perfect with 

 age, and as the animal grows old, he becomes increasingly 

 liable to indigestion from the faulty action of his teeth. 



On an average, a horse takes about 9 minutes to eat I Ib. 

 of oats and about 1 2 minutes to consume the same weight 

 of hay (Colin). 



While food is being chewed, it becomes more or less 



Fig. 4. Jaws of Horse placed evenly together. 



mixed with saliva, which flows into the mouth by tubes from 

 the salivary glands (parotid, submaxillary, and sublingual 

 glands), in response to the stimulus caused by the pre- 

 sence of the food, and which helps the animal to swallow. 

 In horses, the chief source of saliva is the parotid glands, which 

 are of greater comparative size in them than in all other 

 animals, except ruminants. The saliva of the parotid glands 

 consists of about 99.2 per cent, of water. Carpenter points out 

 that the size of the parotid glands in animals is proportionate 



