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A MANUAL OF VETERINARY PHYSIOLOGY 



principles is unaffected by rest or work. The horse absorbs no 

 more per cent, if the diet is increased ; he can extract no more 

 per cent, if the amount be reduced. Feeding experiments 

 show that around 57 per cent, protein and 55 per cent, carbo- 

 hydrates lies the digestive capacity of the horse for these proxi- 

 mate principles in hay. 



If we take the figures for the ox and sheep, for the purpose of 

 comparison, we get the following table : 



These facts are of extraordinary importance in the feeding of 

 animals. The practical conclusions to be drawn from them 

 belong to the realm of hygiene. They are mentioned here 

 owing to their physiological aspect, for though we cannot 

 explain the reason, there is no doubt that both ox and sheep 

 in the matter of food absorption are physiologically superior 

 to the horse, while no animal approaches the pig in the 

 thoroughness with which absorption and consequent utilisation 

 of food substances occurs. 



Absorption of Carbohydrates. — We have seen (p. 256) digestive 

 changes undergone by starch in order to prepare it for absorption, 

 and we have learned that in the body only the simple sugars, 

 such as dextrose, levulose, and galactose, but especially dextrose, 

 are capable of being utilised, while the complex sugars — lactose, 

 cane sugar, and maltose — have all to be reconstructed in order 

 to fit them for absorption. The following brief summary shows 

 by what means the carbohydrates are prepared for entry into 

 the body : 



Starches are converted by means of the saliva and the amylase 

 of pancreatic juice into maltose and dextrin, and then inverted 

 by the ferment maltase into dextrose. 



Lactose requires inversion by lactase into dextrose and galactose. 



Cane sugar requires inversion by invertase into dextrose and 

 levulose. 



If an attempt be made to cause the organism to use up such 

 sugars as cane sugar without passing it through the inverting 

 process, as, for example, by injecting it subcutaneously, it is 

 excreted unchanged in the urine. 



If very large amounts of cane sugar, or even dextrose, be given, 



