14 Feeds and Feeding. 



Smith. 1 states that the ox secretes 112 pounds of saliva daily. 

 In the horse the parotid glands, located at the base of the upper 

 jaw and emptying near the second molar teeth, yield seven- tenths 

 of all the saliva secreted. 



Animals chew their food on one side of the mouth only at a 

 time. It has been found that the parotid gland of the horse yields 

 saliva only on the side where the food is being masticated, the 

 other gland resting until grinding starts up on its side. The 

 chemical composition of mixed saliva, which varies somewhat in 

 different animals, is given for the horse as follows: 



Water 992.00 



Mucus and albumen 2.00 



Alkaline carbonates 1.08 



Alkaline chlorids 4.92 



Alkaline phosphates and phosphate of lime traces. 



1000.00 



The mechanical use of saliva has been mentioned; it serves a 

 second and higher purpose. Saliva contains ptyalin, a soluble 

 ferment which converts the starch of the food into sugar. It acts 

 only upon the starchy matters of the food and not upon the cellu- 

 lose or other constituents. Since the food remains in the mouth 

 a comparatively short time, but little starch can be changed to 

 sugar before the mass is swallowed. The action of the saliva on 

 starch continues in the stomach. 



26. Deglutition. The bolus or rounded mass of food formed by 

 the action of the teeth, the cheeks and the tongue is forced into 

 the oesophagus or gullet and on into the stomach. The gullet of 

 the horse being comparatively small, the boluses do not exceed 

 an inch or an inch and a half in diameter ; in the ox they may 

 be double that size. 



27. Gastric digestion. The stomachs of our domestic animals 

 vary greatly in size, that of the hog holding 7 to 9 quarts, the 

 horse 17 to 19, and the ox over 300 quarts. Colin, who gives the 

 above data, found 145 pounds of air- dry fodder in the first three 

 compartments of the stomach of a cow which had fasted two 



1 Physiology of the Domestic Animals. 



