170 



MOUTH DIGESTION. 



stuffs it comprises, passes immediately from the mouth into the 

 pharynx, and thence through the esophagus into the stomach. 



FIG. 93. Schema showing the temporary and permanent teeth in a child five 

 years old (right side): 1, temporary teeth of the upper jaw; 2, the five temporary 

 teeth of the lower jaw ; 3, 3', permanent median incisors; 4, 4', permanent lateral 

 incisors; 5, 5', permanent canines; 6, 6', the four permanent bicuspids; 7, 7', first 

 molar; 8, second molar of lower jaw in its alveolus (in the upper jaw the second 

 molar is not yet formed) ; 9, inferior dental canal ; 10, orifice of inferior dental 

 canal (after Testut). 



Such food undergoes no chemical changes whatever during this 

 time ; thus, milk, chocolate, and beverages of various kinds are 

 unchanged. If, however, fluids are taken into the mouth when it 

 contains solid food, the latter will be softened by them, and the 



Bicuspids 



Molars Bicuspids Canine Incisors 



FIG. 94. Schema of the two dental arches; view of their external faces, showing 

 their natural relations. 



two will be mixed, and will come under the influence of the agents 

 concerned in carrying on mouth digestion. These agents are the 

 teeth and the salivary glands. 



