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PRINCIPLES OF VETERINARY SCIENCE 



considerable, reaching at most 10 per cent, above the normal 

 average; a similar increase can be produced by the large amount 

 of saliva secreted during mastication of hay or by exercise. The 

 interval before return to the usual lower water content varies 

 individually; in one case it was only ten minutes in duration, but 

 in general appears to be one or two hours. (3) The bulk of the 

 water leaves the stomach quickly. When the stomach is well 



filled, the contents are only 



Oesophagus 



rylorus penetrated very superficially 

 by the water. 



Digestion of hay by the 

 horse was found by Colin to 

 be facilitated when water was 

 allowed with or shortly after 

 feeding. According to Ellen- 

 berger in order for the horse 

 to obtain the fullest possible 

 nutriment from his ration, 

 hay should be fed first, then 

 water, and finally the grain. 

 This practice differs from 

 that usually followed in this 

 country, but is in keeping 

 with the facts already men- 

 tioned relative to the mechan- 

 ism of the stomach. 

 On account of the limited capacity of the horse's stomach, 

 only a portion of a meal can be accommodated at one time. 

 When he is allowed to eat continuously, some food must pass on 

 to the intestines before stomach digestion has been completed. 

 This may result in digestive disturbances of various kinds,- es- 

 pecially colic. 



Another interesting point in regard to stomach digestion is 

 that here starch is converted into sugar, in those animals whose 

 saliva is deficient in ptyalin, by a starch-splitting enzyme that 

 is present in all the small grains high in starch. This fact makes 

 it apparent that grain should not be cooked before being fed. 



Proteins are largely digested in the stomach and small intes- 

 tine. The process of breaking them down is known as putre- 

 faction. It results in the formation of various sharp- smelling 



Fig. 2 9. — Longitudinal section of 

 stomach and contents to show how food 

 is distributed in the stomach. The 

 horse was fed, in turn, (1) 500 grams 

 hay; (2) 750 grams uncolored oats; (3) 

 750 grams colored oats; (4) 500 grams 

 hay. 



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