DIGESTION 



129 



29. Gastric Digestion. What portions of the food are 

 digested in the stomach ? It was formerly thought that all 

 the great changes of digestion were wrought here, but later 

 investigation has taught us better. We now know that the 

 first change in digestion takes place in the mouth, by the partial 

 conversion of starch into sugar. We also know that, of the 

 three organic food principles (considered in Chap. IV.) two 

 the fats and the sugars are but slightly affected by the 

 stomach ; but that its action is confined to that third and very 

 important class from which the flesh is formed, the albuniii 

 A few articles need no preparaHonl)efore enterii 

 as water, salt, and fruit-sugar. These are rapidly taken up 

 by the blood-vessels of the stomach, which everywhere underlie 

 its mucous membrane in an intricate and most delicate network. 

 In this way the function of absorption begins. 



upon the stomach of Alexis St. Martin. It will surprise many to find that 

 vegetable foods they are placed in the latter part of the table require 

 so long a time for their digestion." 



29. What was formerly thought? What do we now know? 

 know ? Water, salt, and sugar ? Absorption ? 



What else do we now 



