356 ITS RESPIRATORY APPARATUS. 



holes.* In man and other mammals the mouth and nos- 

 trils are connected inwardly with a pouch or bag, known 

 as the pharynx, in which both the windpipe and gullet 

 originate ; the former, and anterior, opening from it 

 through an aperture called the glottis; this is covered by a 

 valve, the epiglottis, which usually stands erect, but on 

 the passage of any article turns down like a lid, and gives 

 free ingress to our food. 



In the Cetacea the air-currents pass out of or into the 

 lungs through the spiracles ; but as the mouth is at the 

 same time usually filled with water, it is obvious that 

 some contrivance is necessary to prevent the water from 

 rushing, along with the air in the air-tubes, into the lungs, 

 and producing suffocation. Here we meet with another 

 example of the ingenious adaptation of a mammal to an 

 aquatic life. The epiglottis, or valve, is no longer a 

 simple valve, generally kept open ; but in some species of 

 the Cetacea it is the anterior rim of the rima, or slit, and 

 in others it encloses the base of the pharynx, and assists in 

 forming a proj ecting tube or air-duct. The lower extremity 

 of this air-duct is provided with a circular aperture, sur- 

 rounded by a strong muscle, which unites both the wind- 

 pipe and the air-duct. These intersect the fauces, or 

 " swallow," dividing it into two passages, one for air, and 

 the other for water. 



A naturalist observes, that the whole of this singular 

 mechanism is peculiar to the Cetacea. The other mam- 

 mals, when feeding, are in a medium which, through 

 their respiratory organs, becomes the great vital agent ; 

 but the Cetacea obtain their nutriment always under 



* There are two of these apertures in the. whale, or Balcenidce family ; but 

 one only in the other Cetacea. 



