DIGESTION 261 



pepsin and renin. The latter acts by coagulating milk; the 

 former softens proteids and tends to change them into a kind 

 of fluid called peptone. 



The action of the dilute hydrochloric acid is to neutralize 

 the alkali which is always found in food, and to kill bacteria 

 which would cause fermentation. The acid can also begin 

 the changing of proteids, while pepsin cannot act except 

 in the presence of hydrochloric acid. After digestion in the 

 stomach the food is in a liquid form called chyme. Starches 

 and sugars are digested in the intestines, and it is here that 

 most of the absorption of food takes place. 



References : 



Digestion of Food in the Mouth. 

 Digestion of Food in the Stomach. 

 Digestion of Food in the Intestines. 

 Absorption and Assimilation. 

 Digestion and Absorption. 

 Digestion and Nutrition. 

 Food and Digestion. 

 The Digestive System. 

 Digestion of Food ; the Mouth and the 

 Throat. 



d. 1507 : 112-121. The Absorption of Food. 



e. 1509:96-114. Digestion. 

 /. 1510:55-58. Digestion. 

 g. 1511 : 193-224. Digestion. 



Experiment 84. Digestion of a Proteid. 



Apparatus : Test tubes 6" X f", beaker 200 c.c., ring stand, 

 asbestos mat, burner, thermometer. 



Materials: Pepsin, hydrochloric acid, 10 per cent, cooked 

 white of an egg. 



a. Chop finely a small piece of the egg and place it in a test 

 tube with water. Can you see any change after two hours ? 



