vi HYGIENE OF RESPIRATION 69 



developed chests frequently are. Weak chests may be 

 strengthened by regularly taking proper respiratory 

 gymnastics. 



62. Proper Breathing. The chest may be enlarged 

 up and down by the action of the diaphragm, from 

 front to back by the action of certain muscles of the 

 neck, and from side to side by the use of the muscles of 

 the ribs. Natural breathing exists only when all of 

 these muscles work as they should and cause the chest 

 to enlarge in all of these directions. Tight clothing, 

 bad habits in standing and sitting, and improper school 

 desks work together to deform the chest and decrease 

 its capacity for breathing. Proper breathing makes 

 use of all parts of the lungs. Among civilized people 

 women use the upper part of the lungs chiefly, while 

 men breathe mostly with the lower part ; among savages 

 this difference does not exist. 



63. Alcohol. The nerves controlling the movements 

 of the chest and the size of the blood vessels are easily 

 paralyzed by alcohol. As a result the delicate capillaries 

 of the lungs dilate too much, causing a congestion and 

 inflammation, which tends to diminish the capacity of 

 each little air sac and thus reduce the total lung capacity. 

 A still more serious effect of the habitual use of alco- 

 holic beverages is that alcohol gradually diminishes 

 the power of the capillaries to dilate ; they become less 

 and less responsive to the ordinary stimulation of the 

 nerves. We can now understand why persons who use 

 alcoholic beverages are especially liable to take pneu- 

 monia and other diseases of the lungs. 



