CHAPTER XII 

 DIGESTION 



THE digestive apparatus' consists of the entire 

 alimentary canal, including the mouth, pharynx, 

 esophagus, stomach, small intestines duodenum, 

 jejunum, ileum; large intestines cecum, colon, rec- 

 tum; and the accessory organs, as the teeth, salivary 

 glands, tongue, gastric and intestinal glands, the 

 pancreas, and liver. 



Mastication and Insalivation. Mastication. This is 

 the process whereby the food is chewed or undergoes 

 a mechanic disintegration, which permits of it being 

 properly acted upon by the saliva and formed in such 

 condition to be swallowed; this is brought about by 

 the action of the teeth, tongue, and muscles of masti- 

 cation, which act upon the lower jaw, bringing it 

 with the contained teeth against the upper teeth in 

 the maxilla. 



Insalivation. This is the mixing of the food with 

 the saliva during the act of mastication. The saliva 

 is constantly bathing the mucous membranes of the 

 oral cavity and its contents; however, during mastica- 

 tion there is a marked increase of this complex fluid 

 secreted from the salivary glands parotid, sub- 

 maxillary and sublingual, and palatine glands in the 

 roof of the mouth. 



The Saliva. This is a complex chemic fluid com- 

 posed of the mixed secretions of all the salivary glands. 

 It is a frothy, slightly turbid, viscid fluid. Its reac- 

 tion under normal conditions is alkaline. It may be 

 neutral or acid in some individuals, in which fermen- 



