178 



RESPIRATION 



is taken from the water which is drawn into the mouth and forced 

 out through the gills. Respiration takes place in every living cell, 

 but breathing is only possible in the higher animals that have lungs. 

 The air tubes. The outer openings of the air tubes of man are 

 the nostrils. These lead into two nasal passages terminating in the 

 throat cavity. The nasal passages are specially adapted for pre- 



ironchidl 



^1 Ivrrx^ 



cliaphrag; 



The breathing organs of man are arranged in a continuous passageway from the nostrils 

 to the ends of the bronchial tubes. These tubes subdivide and terminate in air sacs. 



paring air for the use of the body. The hairs in the nose act as a 

 filter, to keep dust and other foreign particles from entering the 

 lungs. The mucous lining absorbs the fine foreign particles and 

 inhibits the development of germs. The mucous lining also 

 moistens the air. Very dry air is irritating to the lungs. 



The air is warmed in the nasal passages by coming in contact 

 with the blood vessels in the linings of the narrow passageways. 

 Air then passes through the glottis into the larynx or voice box. 



