

MOUTH DIGESTION. 151 



lubricated; (5) the soluble part is dissolved, and 

 rendered capable of being tasted ; (6) and part of the 

 starch is converted into soluble sugar by the action 

 of a ferment called ptyalin. 



In the short time occupied by the passage of food through the 

 oesophagus no special change takes place in it, so we may pass on 

 at once to the gastric digestion, which will occupy the next 

 chapter. 



