78. Describe the windpipe. The bronchi. The bronchial tubes. Why is the trachea so called? Describe the structure of the lungs. What are the lungs of slaughtered animals called? Why will a piece of the lungs float on water? 79. Name the wrappings of the lungs. Describe the pleura. How is friction prevented? What are the cilia? Their use? 80. What two acts constitute respiration? In what two ways may the position of the ribs change the capacity of the chest? Describe the process of inspiration. Describe the diaphragm. 81. What is the process of expiration? How often do we breathe? What is sighing? Coughing? Sneezing? Snoring? Laughing? Crying? 82. Describe hiccough. Yawning. Its value? What is meant by the breathing capacity? How does it vary? How much, in addition, can the lungs expel forcibly? How much of the breathing capacity is available only through practice? Value of this extra supply? Can we expel all the air from our lungs? Value of this constant supply? 83. How constant is the need of air? What is the vital element of the air? Describe the action of the oxygen in our lungs. What does the blood give up? Gain? What are the constituents of the air? What are the peculiar properties and uses of each? 84. How can we test the air we exhale? What does its analysis reveal? Which is the most dangerous constituent? What occurs when we rebreathe exhaled air? 85. Describe its evil effects. What is denoted by the "Black Hole of Calcutta"? Give other illustrations of the dangers of bad air. Describe the need of ventilation. Will a single breath pollute the air? 86-95. How can we detect the floating impurities in the air? What is the influence of a fire or a light? Of a hot stove? When is the ventilation perfect? What diseases are largely owing to bad air? Should the windows and doors be tightly closed, if we have no other means of ventilation? Is not a draught of air dangerous? How can we prevent this, and yet secure fresh air? What is the general principle of ventilation? Must pure air necessarily be cold air? Are schoolrooms always properly ventilated? What is the effect? Are churches? Are our bedrooms? Should children or delicate people sleep in cold rooms? Can we, at night, breathe anything but night air? Is the night air out of doors ever injurious? _Ans_. In times and places of malaria, and also in very damp weather, it should be avoided, even at the risk of bad air in doors. Describe some of the wonders of respiration. 96. How is constriction of the lungs produced? When may clothing be considered tight? What are the dangers of tight lacing? Which would make the stronger, more vigorous, and longer-lived person, the form shown in _A_ or _B_, Fig. 33? Is it safe to run any risk in this dangerous direction?