CHAPTER V 

 DIGESTION 



Section i. 



Digestion in the Mouth. 



Prehension of Food. — The methods by which animals convey 

 food to the mouth differ according to the species. In the horse 

 the lips play an important part, for which purpose they are thick, 

 mobile, remarkably strong, and endowed with acute sensation ; 

 in the ox they serve a subordinate function, being rigid and 

 wanting in mobility ; in the sheep the upper lip is cleft in such 

 a manner as to divide it completely into two parts, each possess- 

 ing independent movement ; in the pig the lower lip is pointed 

 and the upper one insignificant. 



In manger feeding the horse collects the food with the lips, 

 but in grazing cuts off the grass with the incisor teeth, drawing 

 the lips back in order that they may bite closer to the ground. 

 In the ox the tongue is protruded and curled around the grass, 

 which is thus drawn into the mouth and taken off between the 

 incisor teeth and the dental pad. In the sheep the divided 

 upper lip allows of the incisors and dental pad biting close to 

 the ground, so that animals of the sheep and goat class can live 

 on land where others such as the horse and ox would starve. 

 In whatever way the food is cut off, it is carried back by the 

 movements of the tongue to the molar teeth, there to undergo 

 a more or less complete grinding. 



In the ox and sheep the incisor teeth move freely in their 

 sockets ; the object of this is to prevent injury to the dental 

 pad, for which purpose also they are placed very obliquely in 

 the jaw. In the horse the incisor teeth in early life are very 

 upright, but become oblique with age. The molars in all herbi- 

 vora are compound teeth ; in the horse they are very large, 

 especially those in the upper jaw. Being composed of materials 

 of different degrees of hardness they wear with a rough surface, 

 which is very essential to the grinding and crushing the}' have 



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