168 THE VITAL PROCESSES 



supply water which acts as a solvent and carries the active 

 chemical agents, or enzymes, that convert the insoluble 

 foods into substances that are soluble. The muscles in 

 the walls of the canal perform the mechanical work of 

 digestion, while the nervous system controls and regulates 

 the activity of the various organs concerned in this work. 



Exercises. I. State the general purpose of digestion. How does 

 digested food differ from that not digested ? 



2. Name all the divisions of the alimentary canal in the order in 

 which the food passes through them. 



3. What other work besides digestion is carried on by the alimentary 

 canal ? 



4. What is gained by the mastication of the food ? Why should 

 mastication precede the other processes of digestion ? 



5. What is the work of the tongue in digestion ? 



6. State the purposes served by the gastric juice. 



7. Give reasons for regarding the small intestine as the most im- 

 portant division of the food canal. 



8. Atwhat places, and by the action of what liquids, are fats, pro- 

 teids, and starch digested ? 



9. What enzymes are found in the pancreatic juice ? What is the 

 digestive action of each ? 



10. Describe the work performed by the muscles of the stomach, the 

 mouth, the esophagus, and the small intestine. 



n. What' advantages are derived from the use of cooked food ? 



12. State the advantages of drinking pure water. 



13. If all the food that one needs to take at a single meal can be 

 thoroughly masticated in fifteen minutes, why is it better to spend 

 a longer time at the table ? 



14. What is meant by the overlapping of meals ? What bad results 

 follow ? How avoided ? 



PRACTICAL WORK 



Examine a dissectible model of the human abdomen (Fig. 75), noting 

 the form, location, and connection of the different organs. Find the 

 connection of the esophagus with the stomach, of the stomach with 

 the small intestine, and of the small intestine with the large intestine. 



