CHAPTER VII 

 THE DIGESTION OF FOOD 



THE food we eat is destined to become blood, bone, muscle, 



nerve, etc. But before food can become part and parcel of our 

 bodies, it must be digested ; that is, it must be so softened^ dis- 

 solved, and chemically changed that it can pass through the walls 

 of the alimentary canal and reach the vessels which carry it to 

 the different parts of the body. The alimentary canal (Fig. 41) 

 in which food is digested or made ready 

 for absorption into the blood consists 

 principally of mouth, stomach, intestines, 

 and of the glands which pour secretions 

 into these organs. The salivary glands 

 which open into the mouth, the gastric 

 glands in the stomach, the intestinal 

 glands in the intestines, and the liver and 

 pancreas glands which open into the 

 intestine, secrete chemical compounds 

 called ferments. These ferments act upon 

 carbohydrates, proteins, and fats and 

 change them into substances which can 

 pass through cell walls and be absorbed 

 by the blood. If the digestive glands 

 fail to supply ferments, the food we eat 

 lies undigested in the alimentary canal 

 and is worthless for cell growth and repair. In the normal 

 healthy body the various glands send abundant secretions into 

 the alimentary canal, and the food is soon changed into sub- 



9> 



41 . The alimentary 

 canal - 



