RESPIRATORY CHAMBERS 



135 



drier the air, the more the moisture added to it. In the 

 upper storey of the chamber, too, is set a very marvellous 

 nerve mechanism — one which samples the air as it enters, 

 and quickly discovers if there is in it anything which may 



BASE of SKULL 



SOFT 

 PALATE 



TONS/L 



eP/GLOTTiS 



LARYNX 



TRACHEA 



CESOPHAQUS 



Fig. 33.— The air passages in the nose, throat, and mouth exposed. 



prove injurious to the delicate lining of the respiratory 

 chambers. Having been partly warmed as it rushes 

 through the nasal cavities, the breath then enters the 

 throat or pharynx — a wide open channel into which the 

 cavity of the mouth also opens (fig. 33) ; hence when 



