The essentials of healthA text-book of anatomy, physiology, hygiene, alcohol, and narcotics . be is completed by a thin mem-brane. The rings are placed one over the other, sepa-rated only by a narrow membrane. They keep thetrachea from collapsing ; thus always insuring a freepassage for the air. The tube is lined, its whole length,with a mucous membrane. About opposite the upperpart of the sternum, the trachea divides into twobranches, called the bronchi, one branch going to eachlung. The Bronchi and the Air Cells. After entering thelungs, the bronchi divide again and again, until theyare very
The essentials of healthA text-book of anatomy, physiology, hygiene, alcohol, and narcotics . be is completed by a thin mem-brane. The rings are placed one over the other, sepa-rated only by a narrow membrane. They keep thetrachea from collapsing ; thus always insuring a freepassage for the air. The tube is lined, its whole length,with a mucous membrane. About opposite the upperpart of the sternum, the trachea divides into twobranches, called the bronchi, one branch going to eachlung. The Bronchi and the Air Cells. After entering thelungs, the bronchi divide again and again, until theyare very minute in size. They are everywhere linedwith a mucous membrane. A study of Fig. 41 willmake these facts more simple. At 1, is the epiglottis,standing guard over the entrance to the air passagesbelow ; at 2, is the larynx, or voice box; at 3, is thetrachea with its rings of cartilage; at 4, is the right RESPIRATION. 129 lung, so drawn that the bronchial tubes can be seenwithin it. After these have become very small, from their re-peated divisions, they terminate in a collection of minute. Fig. 41. The respiratory apparatus : (1) the epiglottis; (2) the larynx ;(3) the trachea ; (4) the right lung ; (5) the left lung. sacs, called air cells. The walls of these air cells arevery thin and highly elastic. They can be distended byslight force, and when the force is removed, they can atonce resume their former size. Fig. 42 shows a terminal 9 130 THE ESSENTIALS OF HEALTH.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysiology, bookyear1
