112 OUR BODIES AND HOW WE LIVE 



159. The Action of the Gastric Juice. The gastric juice 

 consists of water with a little hydrochloric acid and two 

 ferments called pepsin and rennin. The pepsin, acting in 

 the presence of a weak acid, turns the proteid food stuffs 

 into what are called peptones, which are soluble and capa- 

 ble of being absorbed into the blood. 



The gastric juice has no action on starchy foods, neither 

 does it act on fats, except to set free the fat from the 

 connective tissue which contains it. 



Experiment 35. To show the action of gastric juice on milk. Mix 

 two teaspoonfuls of fresh milk in a test tube with a few drops of 

 artificial gastric juice, 1 and keep at about 100 F. In a short time 

 the milk curdles so that the tube can be inverted without the curd 

 falling out. By and by whey is squeezed out of the clot. 



160. Passage of the Food into the Intestines. After two 

 or three hours of digestion, the food in the stomach is 

 reduced to a pulpy and almost fluid condition. It now 

 takes on the appearance of pea soup, usually of a grayish 

 color, and is called chyme. 



After one to four hours, the chyme begins to move on 

 in successive portions into the first part of the small intes- 

 tine. The ringlike muscles of the pylorus relax at inter- 

 vals to allow the muscles of the stomach to force the partly 

 digested mass into the intestines. 



This action is often repeated until even the indigest- 

 ible masses which the gastric juice cannot break down are 

 crowded out of the stomach into the intestines. From three 

 to four hours after a meal the stomach is quite emptied. 



1 An artificial gastric juice may be obtained for experimental purposes 

 by dissolving about ten grains of pepsin powder (made by some reputable 

 manufacturer and obtained of any druggist) in half a pint of water and 

 adding perhaps from fifteen to twenty drops of strong hydrochloric acid, or 

 about six times as much of the dilute acid. 



