372 HOW FOOD IS PREPARED FOR BODY USE 



are soluble in water. This is due to the action of the enzyme 

 pepsin. 



The hydrochloric acid found in the gastric juice acts upon lime 

 and some other salts taken into the stomach with food, changing 

 them so that they may pass into the blood and eventually form 

 the mineral part of bone or other tissue. This acid also has a 

 decided antiseptic influence in preventing growth of bacteria, some 

 of which cause decay, others of which cause disease. 



Experiments on digestion in the stomach. Some very interest- 

 ing experiments have been made by Professor Cannon of Harvard 

 with reference to the movements of the stomach contents. Cats 

 were fed with a material having in it subnitrate of bismuth, a 

 harmless chemical that is visible under the fluoroscope. It was 

 found that shortly after food reached the stomach, a series of 

 waves began which sent the food toward the pyloric end of the 

 stomach. If the cat was feeling happy and well, these contrac- 

 tions continued regularly, but if the cat was cross or bad tempered, 

 the movements would stop. These experiments were repeated on 

 men, with like results, and show the importance of cheerfulness 

 at meals. Pleasant conversation and a cheerful mind at the table 

 will go far toward making the food taste better and also toward 

 causing it to digest properly. 



Other experiments showed that food which was churned into 

 a soft mass was permitted to leave the stomach only when it 

 became thoroughly permeated by the gastric juice. It is the 

 acid in the partly digested food that causes the pyloric ring of 

 muscle to open and allow the food to escape little by little into the 

 small intestine. 



Self-Testing Exercise 



The food passes through the (1) and (2) by a series 



of (3) (4). The stomach is a (5) organ. 



The (6) (7) secrete a (8) which empties 



into the (9). This (10) is slightly (11) in 



chemical reaction, and contains two enzymes, (12) and 



(13). The enzyme (14) digests the (15) 



in the stomach. Our digestion is affected by our (16). 



