food and water, and thus helps to protect us from disease germs.

The liver and the pancreas. The liver, which weighs nearly four pounds, lies on the right side of the body, opposite the stomach. It makes a greenish yellow liquid called bile. This liquid flows into the small intestine through a duct from the liver and assists in the digestion of food. The pancreas is a long, flat organ that lies below the stomach. It has a duct that joins the duct from the liver and empties into the small intestine. The juice from the pancreas does a very important part of the work of digesting the foods in the small intestine.

The small intestine. All along in the walls of the small intestine are little glands that pour out juices to assist in the digestion of the food. The food moves slowly through the small intestine, which is more than twenty feet long, requiring some four or five hours to complete this part of its journey.

Digestion in the small intestine. After the food passes from the stomach into the small intestine, the juices from the liver and pancreas are poured in with it, and the juices from the intestinal glands also are mixed with it. As the food moves slowly along the intestine, the juices finish the process of digestion. The food then soaks through into the great network of little blood vessels that are in the wall of the intestine, and is carried all through the body. Thus the solid food that we eat is dis

solved and taken into the body to nourish all its parts.

The large intestine. In all food there is some refuse matter like the woody matter in cabbages and potatoes, the skins of fruits, and the tough fibers of meats. This matter passes on into the large intestine. Nothing is more important to the health than

FIG. 16. The lining of the small intestine is thickly covered with little finger-like structures called villi. The digested food is absorbed into the blood vessels that are in these structures. The picture shows villi highly magnified.

that this refuse matter be cleared out of the large intestine every day and not allowed to lie in the intestine to sour and decay.

organs.

The importance of caring for the digestive The work of digesting the food is so important that the organs that do this work fill nearly the whole cavity of the body. "It is not what we eat but what we digest that makes us strong." This

is an old saying, and it is a true one. We cannot have strong bodies if we do not have healthy digestive organs to prepare food for them. In the next chapter we shall study some ways of keeping the digestive organs in health.

Questions: 1. What do the digestive juices do to the foods during digestion? 2. What digestive juice is found in the mouth? 3. Where does it come from? 4. How many pairs of salivary glands are there? 5. Where are they found? 6. Give two uses of the stomach. 7. What kind of foods does the gastric juice digest? 8. What does the acid in the gastric juice do? 9. Where is the liver found in the body? 10. How large is it? II. What liquid comes from it? 12. Where in the body is the pancreas? 13. Into what is the juice from the pancreas emptied? 14. How long is the small intestine? 15. What is found along its walls? 16. How long does it take the food to pass through the small intestine? 17. What is happening to the food while it makes this journey? 18. Where does the food go after it has been digested? 19. What part of our food goes on into the large intestine? 20. Why is it important for us to care for our digestive organs?

Suggestions and topics for development: Where the gastric juice comes from, and what habits the pupils have that may interfere with the flow of it. Work out the continuous story of the movements and digestion of food in the alimentary canal. Illustrate absorption by showing how salt or sugar dissolved in water will pass through a paper. Show digestion by putting a cube of hard boiled white of egg into a glass of water with a few drops of acid and a little pepsin. The lining of a calf's stomach dried and pulverized may be used instead of pepsin. Prepare materials in another glass in the same way, but first cut the egg into fine pieces to show the advantages of thoroughly chewing food. Set both glasses in a warm place (about 100 degrees is best) for a few hours.

KEEPING THE DIGESTIVE ORGANS IN HEALTH

To a great extent life is colored by the way the digestive organs do their work. "If to do were as easy

FIG. 17. William Ewart Glad

as to know what were

good to do, chapels had been churches and poor men's cottages princes' palaces. It is a good divine that follows his own instructions: I can easier teach twenty what were good to be done than be one of the twenty to follow mine own teaching."

The above quotation

stone, who was called "England's is from Shakespeare. It Grand Old Man." He believed is inserted here to start that his vigorous old age was in

large part due to his habit of you on the study of cutting his food into small pieces this chapter with the and chewing it thoroughly. idea that it will require

doing as well as knowing to keep your digestive organs in health.

Exercise and the digestive organs. Physical exercise gives the muscles and nerves a tone and a vigor that they lack without it. The digestive organs seem to catch this vigor from the muscles and nervous system; for when we exercise they digest almost anything we may eat without difficulty.

On the other hand, if we allow our muscles to become soft and flabby, our digestive organs also will lose their tone and become sluggish in their work. Vigorous games, sports like running, rowing, hill-climbing, swimming, skating, and riding, and spirited labor are what is needed to key the body up to the proper state for work. The excitement and thrill of the work or play is a necessary part of the exercise; and gentle walking, mild games, or plodding labor will not serve the same purpose.

The importance of thoroughly chewing the food. People who make it a rule to chew every mouthful of food into a perfect paste find that their health is very greatly improved by doing so. Just as sugar dissolves more quickly in a glass of water when it is in fine grains than when it is in large, hard lumps, so food ground into bits by the teeth is digested and dissolved more quickly in the stomach and intestine than food that has been swallowed in large pieces. Thorough chewing of the food carries us far on the way to a good digestion, and a good digestion sets us well on the road to good health.

Drinking liquids at meals. A glass or two of water taken at mealtime in small sips moistens the food and helps to mix the saliva with it, thus causing the starch to be more quickly digested. Water taken in larger amounts hinders digestion, especially if the food is washed down without being properly chewed. The water should not be ice cold,