SALIVARY AND GASTRIC DIGESTION 203 



product. This is very like what takes place in the sour- 

 ing of milk, and, indeed milk may be soured in the 

 stomach within a very short interval. Lactic acid is 

 not harmful unless in uncommon amounts; many people 

 who make use of buttermilk or other beverages contain- 

 ing it believe that it is beneficial. 



Summary. The stomach serves, first of all, as a place 

 for storage and to maintain a gradual delivery to the 

 intestine. The antrum has an action adapted to pro- 

 mote the mechanical reduction of the food. Salivary 

 digestion of starch proceeds in the stomach until the 

 acidity is everywhere established. True gastric diges- 

 tion affects proteins chiefly and is incomplete. There 

 is some digestion of well-emulsified fat. The mixture 

 passing the pylorus two or three hours after a mixed 

 meal may be expected to contain peptones derived from 

 the proteins, dextrins and sugar from the starch, traces 

 of glycerin and fatty acids from fats, portions of all the 

 foods undigested, hydrochloric acid from the gastric 

 juice, and lactic acid produced by fermentation. Except 

 for particularly resistant particles it will be smooth and 

 creamy. 



