1/4 SNEEZING AND COUGHING. 



cles which have pulled up the ribs and sternum (to cause 

 inspiration) relax, and these bones fall back into their 

 former places. The diaphragm also relaxes, and the 

 liver, stomach, and intestines, pressing against its under- 

 side, then push it up towards the chest. Thus the lungs 

 are squeezed and air driven out of them. 



24. Sneezing and Coughing. The mucous membrane 

 lining the nose and the larynx is very sensitive. Any- 

 thing irritating- it causes a peculiar kind of violent ex- 

 piration, calculated to drive a powerful blast of air 

 through the air-passages and force away the irritant. 

 When the inside of the nose is tickled, a sneeze follows. 

 The irritation makes us first draw a deep breath, with- 

 out our willing it at all, and in spite of our will if we try 

 to prevent it. Then, when the lungs are filled with air, 

 the glottis (p. 169) is closed and the chest compressed. 

 Next, the glottis is suddenly opened and the compressed 

 air rushes out of the lungs. It is made to go through 

 the nose, because the root of the tongue and the soft 

 palate are brought together, so as to close the opening 

 from the pharynx to the mouth. Sneezing is a good 

 example of the resemblance of our bodies in many ways 

 to machines, made to do a certain thing under certain cir- 

 cumstances. The control which we have over them by 

 our will is not at all complete. We can neither prevent 

 a sneeze when the nose is irritated, nor make even a 

 good imitation of a real sneeze when it is not. 



A cough differs from a sneeze, mainly in the fact that 

 the air is allowed to pass out through the mouth. Its 

 use is to drive out anything irritating the larynx. 



24. What results when the mucous membrane of nose or larynx is 

 irritated ? Describe the process of sneezing ? What may we learn 

 from it ? Of coughing ? Its use ? 



