128 



THE HUMAN BODY. 



Fig. 50. 



SECTION OF NASAL FOSSAE, SEEN FROM 

 BEHIND. 



rated by a partition. They are narrow, but quite exten- 

 sive. They enter into the upper part of the throat by 

 two openings, like the two on the face. Above, they con- 

 nect with cavities in the 

 forehead, and at the sides 

 with cavities in the upper 

 jaw-bones, and with the 

 eye. These passages and 

 cavities are lined with 

 mucous membrane; and 

 when this is inflamed, as 

 in a cold in the head, we 

 have a feeling of fullness, 

 not only in the nose, but 

 also in the forehead and 

 eyes. 



3, The nerves of smell are up in the top of the nasal 

 cavities. In ordinary breathing, the air passes straight 

 back to the throat; but, when we wish to smell any 

 thing distinctly, we sniff suddenly, and so draw the air 

 up to the top of the cavities, with the odorous particles 

 in it. 



4, The odorous particles will diffuse themselves through 

 the cavities, and reach the nerves, without this sniffing, 

 unless they are few and faint. But, by sniffing the air, 

 we get the sensation more quickly and keenly. 



5, A horse can not breathe through his mouth, but a 

 man can. We do so when the nose is stopped, and when 

 we are breathing rapidly, as in exercise. Some always 

 do so when asleep. 



It is better to breathe through the nose, because, 

 1. The nasal cavities being narrow, the air is spread out 



