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 CHAPTER VI

THE RESPIRATION

Experiment 1. (Home.) Study of the Throat.—Sit with the back to the light. Study the open mouth and throat with a mirror and make out the uvula, tonsils, and other parts shown in Fig. 68.

Experiment 2. Anatomy of Lungs.—Study fresh lungs of sheep, hog, fowl, or frog. Will they float? Will they contract when expanded by air blown in through a quill or other tube? What is the structure of the windpipe? Can you distinguish the arteries from the veins by the stiffness of their walls? Which contain pure blood? Study branching of air tubes. Make a sketch.

Experiment 3. Tests of Expired Air.—Breathe upon a mirror, bright knife blade, or cold window pane. Result? State your conclusion? Experiment 4.—Carbon dioxid added to limewater will cause a white cloud consisting of particles of limestone. Breathe through a tube or straw or the hollow stem of a reed into clear limewater. Result? Conclusion? (Limewater may be had at druggist's or made by pouring water upon a lump of unslackened lime and draining it off when lime has settled.) Experiment 5. Breathe for several minutes upon the bulb of a thermometer. Result? Conclusion? Experiment 6. Breathe a few times into a large, carefully cleaned pickle jar, or a bottle. Cork it tightly, and set it in a warm place for several days. Then uncork and smell the air in it. Result? Conclusion? Experiment 7. Pierce a small hole in a card, place card over a wide-mouthed bottle, and breathe into bottle through a tube, lemonade straw, or hollow reed. Pull out straw. Place bottle, mouth downward, on table, and slip out card. Slide bottle to edge of table and lift lighted candle into bottle. Result? Experiment 8. Place bottle of fresh air over lighted candle. Result? Conclusion? (See Animal Biology, p. 14.)

Experiment 9. (School.) Testing the Air of a Room.—Fill a fruit jar or large bottle with water, and take it into a room containing many people. Pour out the water. (This insures that all the air now in the jar is air obtained in the room to be tested.) Seal the jar if test is not to be made at once. Test by pouring in two tablespoonfuls of clear limewater and shake. If the limewater turns milky, the ventilation is bad.

Experiment 10. (Home and school.) Homemade Current Detector.—Dangle a bit of paper by means of a spider web or thread from the