6. _Asphyxia_ (as-fix'-i-a).--When a person is drowned, strangled, or choked in any way, what is called asphyxia occurs. The face turns black; the veins become turgid; insensibility and often convulsions ensue. If relief is not secured within a few minutes, death will be inevitable. [Footnote: The lack of oxygen, and the presence of carbonic-acid gas, are the combined causes. Oxygen starvation and carbonic-acid poisoning, each fatal in itself, work together to destroy life.] (See p. 264.) 7. _Diphtheria_ (_diphthera_, a membrane) is characterized by fever, debility, and a peculiar sore throat, in which exuding fibrinous matter forms a grayish white membrane, which afterward decomposes with a fetid odor. Its sudden and insidious approach, contagious character, and frequent fatality, render it an exceedingly dreaded disease. A diphtheritic patient should be quarantined, and everything connected with the sick room thoroughly disinfected. 8. _Croup_, which often attacks young children, is an inflammation of the mucous membrane of the larynx and trachea. It is commonly preceded by a cold. The child sneezes, coughs, and is hoarse, but the attack frequently comes on suddenly, and usually in the night. It is accompanied by a peculiar "brassy," ringing cough, which, once heard, can never be mistaken. It may prove fatal within a few hours. (See p. 260.) 9. _Stammering_ depends, not on defects of the muscles, but on a want of due control of the mind. When a stammerer is not too conscious of his lack, and tries to form his words slowly, he speaks plainly, and may sing well, for then his words must follow one another in rhythmic time. Many persons who stammer in common conversation can talk with fluency when making a speech. The stammerer should seek to discover the cause of his difficulty, and to overcome it by vocal and respiratory exercise, especially by speaking only after a full inspiration, and during a long, slow expiration. PRACTICAL QUESTIONS. 1. What is the philosophy of "the change of voice" in a boy? 2. Why can we see our breath on a frosty morning? 3. When a law of health and a law of fashion conflict, which should we obey? 4. If we use a "bunk" bed, should we pack away the clothes when we first rise in the morning? 5. Why should a clothespress be well ventilated? 6. Should the weight of our clothing hang from the waist, or the shoulder? 7. Describe the effects of living in an overheated room. 8. What habits impair the power of the lungs? 9. For full, easy breathing in singing, should we use the diaphragm and lower ribs, or the upper ribs alone? 10. Why is it better to breathe through the nose than the mouth? 11. Why should not a speaker talk while returning home on a cold night after a lecture? 12. What part of the body needs the loosest clothing? 13. What part needs the warmest? 14. Why is a "spare bed" generally unhealthful? 15. Is there any good in sighing? 16. Should a hat be thoroughly ventilated? How?