THE DIGESTIVE SYSTEM 69 



A viscus is any large interior soft organ of the body. Abdomi- 

 nal viscera are the organs comprising the digestive system con- 

 tained in the abdominal cavity. 



THE ORGANS OF DIGESTION 



The organs of digestion may be conveniently grouped into 



Alimentary Organs: Accessory Organs: 



1. Mouth 1. Tongue 



2. Pharynx 2. Teeth 



3. Esophagus 3. Salivary glands 



4. Stomach 4. Liver 



5. Small intestine 5. Pancreas 



6. Large intestine 6. Intestinal glands 



The mouth is a cylindric cavity situated between the two jaws, 

 elongated in the direction of the long axis of the head. It has an 

 anterior opening for the introduction of food, and a posterior 

 one that communicates with the pharynx. When closed, the 

 mouth is nearly filled up by the teeth and tongue. It is guarded 

 in front by the lips and laterally by the cheeks. 



The lips are designated superior and inferior from their posi- 

 tions. On the outer surface of the lips are found many fine, 

 short hairs; also a number of long bristle-like hairs of a tac- 

 tile nature. The inner surface is lined with mucous membrane 

 which is smooth and usually of a pink color in the horse. In the 

 ox the middle part of the upper lip is termed the muzzle. It is 

 smooth, cool, and moist in health. 



The cheeks are two membranous walls which form the sides 

 of the mouth. They are continuous in front with the lips; 

 above and below, with the gums. Numerous secreting glands 

 are found in the substance of the cheeks. In the horse the inner 

 surface is smooth, but in the ox many file-like elevations, termed 

 papillae, stud it. 



The tongue extends from the back part of the mouth to the in- 

 cisor teeth. It is a freely movable muscular organ. Some of 

 its muscles are directed longitudinally, others vertically, and still 

 others transversely. This arrangment affords the organ extensive 

 movements in all directions. A fold of membrane, the franum, 

 connects the inferior surface with the floor of the mouth. For 

 description, it may be divided into tip, body, and root. The 



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