HYGIENE OF RESPIRATION 1 6$ 



enlargement through glandlike growth of a structure in 

 the upper part of the pharynx called the third tonsil. It 

 is just behind the posterior openings of the nasal passages, 

 and can be easily removed if it becomes enlarged. Per- 

 sons who sleep with the mouth open are likely to snore, 

 and the mouth and throat are always dry in the morning. 



273. Do the Breathing Muscles rest? Expand your 

 lungs, and see whether they will contract of themselves. 

 Contract your lungs and see whether they will expand of 

 themselves. See whether you can make waist, chest, and 

 abdomen expand at the same time. You learned that the 

 periods of rest taken by the heart muscles amount to how 

 many hours daily ? The breathing muscles also rest a con- 

 siderable portion of the time ; with calm and happy people 

 they rest more than with people of anxious, unquiet disposi- 

 tions. We can breathe by means of the expiratory muscles 

 alone or by means of the inspiratory muscles alone, or by 

 using each set alternately. When all the breathing muscles 

 are relaxed, the lungs are at rest in what may be called the 

 neutral position, since there is neither voluntary contrac- 

 tion nor expansion. In this position they are of about aver- 

 age size. If now we use the expiratory muscles and contract 

 the lungs, the muscles may relax during inspiration which 

 follows, for it will be accomplished by the elasticity of the 

 abdominal walls and organs, and of the cartilages of the 

 thoracic cage ; for these were bent when the cage was 

 pulled from the neutral position. Try this method of 

 breathing for a few minutes. 



274. Or, on the other hand, when the lungs are at rest 

 we may breathe by using the inspiratory muscles (Fig. 139) 

 (diaphragm, external intercostals, etc.), thus expanding the 

 lungs from the neutral position, and allowing the muscles 

 to rest, while the elasticity of the parts forces out the air. 

 Try breathing in this way. 



275. This expanded breathing has the advantage over 



