LUNG CAPACITY. 117 



are modifications of respiration connected with certain emo- 

 tions. Yawning and sighing are deeper breathings, caused 

 by ennui, depressing emotions, or a deficient ventilation. Hic- 

 cuping is sudden inspiration, produced by spasmodic action 

 of the diaphragm, accompanied by sudden closure of the 

 glottis, and is often caused by some disorder of stomach 

 digestion. Snoring is caused by breathing through the mouth, 

 and setting the soft palate into vibration. Sniffing is sudden 

 inspiration : the diaphragm is suddenly pulled down, the air 

 in the nasal cavity is thus drawn downward, and the air we 

 wish to test, or the odor we wish to inhale, is thus drawn into 

 the upper nasal cavities ; whereas in ordinary inspiration most 

 of the air passes along the lower part of the nasal passage. 

 In hawking, the air is forced out through the narrowed pas- 

 sage between the root of the tongue and the soft palate to 

 remove mucus. Gargling is forcing air up through liquid 

 held between the tongue and the soft palate. 



Capacity of the Lungs. Have the class stand, and each 

 pupil hold up his right hand. 



1. Let all breathe together, at the ordinary rate and depth, 

 and let the hand rise about three inches during inspiration, 

 and fall again during expiration. The amount of air taken 

 in at an ordinary breath is from 20 to 30 cubic inches, or 

 about a pint. This is called the Tidal Air. 



2. As before, let the hand go up and down with the breath- 

 ing, but at the end of the third inspiration, instead of stopping 

 with the usual amount, keep on breathing in as much as pos- 

 sible, letting the hand rise accordingly. This air that can be 

 taken in above the ordinary breath is called the Complemental 

 Air, and it is estimated to be, on the average, about 120 cubic 

 inches. 



3. Begin as before, and at what would be the end of the 

 third expiration continue to drive out as much air as possible, 



