SCIENCE OF COMMON THINGS 123 



" What is sneezing? Laughing. Crying. Suffocation. 



strikes against the surrounding air ; this makes a report 

 in the same way as when any two solids (such as your 

 hand and the table) come into collision. 



77 What is sneezing f 



Sneezing is a phenomenon resembling cough ; only 

 the chest empties itself at one effort, and chiefly 

 through the nose, instead of through the mouth, as in 

 coughing. 



777 What is laughing! 



Laughing consists of quickly repeated expulsions of 

 air from the chest, the glottis being at the time in a 

 condition to produce voice ; but there is not between 

 the expirations, as in coughing, a complete closure of 

 the glottis. 



773 What is hiccough f 



Hiccough is the stopping of the commencement of a 

 strong inspiration, by a sudden closing of the glottis. 



779 What is crying ? 



Crying differs from laughing almost solely in the 

 circumstance of the intervals between the gusts or expi- 

 rations of air from the lungs being longer. Children 

 laugh and cry in the same breath. 



780 Why, in straining to lift weights, or to make any powerful bodily 

 effort, do we compress our breath ? 



We shut up the air in the lungs in order to give 

 increased steadiness and firmness to the body. 



781 When is a person suffocated? 



When the windpipe becomes choked, or the supply of 

 air to the lungs is in any way cut off. 



783 Why do birds sing comparatively louder -than man f 



Because the strength of the larynx, and of the muscles 

 of the throat, in birds, is infinitely greater than in the 

 human race. The loudest shout of man is but a feeble 

 cry compared with that of the golden-eyed duck, the 

 wild goose, or even the woodlark. 



783 How are winged insects generally found to produce sound f 



Generally they excite sonorous vibrations by the 



