STOMACH AND INTESTINAL DIGESTION 23 



It is a wonderfully elastic, muscular bag, having an 

 inside lining that admits of great expansion. In 

 various parts of this lining is situated the second set 

 of chemical workshops that help to accomplish diges- 

 tion. These tubes or glands secrete a fluid called 

 gastric juice, the three most important ingredients of 

 which are pepsin, hydrochloric acid, and rennin. 



What part has the gastric juice in the wonderful 

 process of making body building material from food? 

 It digests the proteid parts. While starch and fat 

 become more liquefied, passing from the stomach with 

 other substances in the. form of a grayish white sub- 

 stance called chyme, they are not digested, excepting 

 the action of saliva on starch, until acted upon by the 

 secretions of the intestines. 



Must we depend upon doctors and books for 

 the information that gastric juice digests proteids, 

 or can we prove the fact ourselves ? An ounce of water 

 mixed with twelve drops of hydrochloric acid and one 

 grain of pepsin will completely dissolve the cooked 

 white of an egg in two hours, at the ordinary tem- 

 perature of the stomach, which is about ninety-nine 

 and one-half to one hundred degrees. A mixture of 

 five grains of pepsin, eighteen drops of strong hydro- 

 chloric acid, and six ounces of water is very like a 

 similar quantity of gastric juice. If a piece of meat 

 is placed in this mixture and left for two hours or 

 more, at a temperature of ninety-nine and one-half 

 degrees, it will be changed to liquid form. 



