the mechanical work of digestion, while the nervous system controls and
regulates the activity of the various organs concerned in this work.

Exercises.—1. 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 important
division of the food canal.

8. At what places, and by the action of what liquids, are fats, proteids,
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.