THE SPECIAL SENSES 281 



the interior of the nose. That prominent feature of the face, 

 the nose, which is merely the front boundary of the true nasal 

 uLruii, is composed partly of bone and partly of cartilage. The 

 upper part of it is united with the skull by means of a few 

 small bones, to which circumstance is due its permanence of 

 shape. The lower portion, or tip of the nose, contains several 

 thin pieces of cartilage, which render it flexible and better able 

 to resist the effects of blows and pressure. Behind the nose we 

 find quite a spacious chamber, separated from the mouth by 

 the hard palate, forming the " roof of the mouth," and also by 

 the soft palate (see Fig. 62) ; and divided into two cavities by a 

 central partition running from before backward. 



39. These nasal cavities, constituting the true beginning of 

 the air-passages, extend from the nose backward to the upper 

 opening of the throat, and rise as high as the junction of the 

 nose with the forehead. The inner wall of each cavity is 

 straight and smooth ; but from the outer wall there jut into 

 each cavity three small scroll-like bones. The structure of 

 these bones is very light, and hence they have been called the 

 " spongy " bones of the nose. In this manner, while the extent 

 of surface is greatly increased by the formation of these wind- 

 ing passages, the cavities are rendered extremely narrow; so 

 much so, in fact, that a moderate swelling of the mucous mem- 

 brane which lines them, as from a cold, is sufficient to obstruct 

 the passage of air through them. 



40. The Nerve of Smell. The internal surface of the nasal 

 passages is covered by a delicate and sensitive mucous mem- 

 brane. Its surface is quite extensive, following as it does all 

 the inequalities produced by the curved spongy bones of the 

 nose. Only the upper portion of it is the seat of smell, since 

 that part alone receives branches from the "first pair" of 

 cranial nerves, or the olfactory nerve, which is the special 

 nerve of smell (see Fig. 62). In Fig. 62 is shown the distribu- 

 tion of this nerve, in the form of an intricate network upon the 

 two upper spongy bones. The nerve itself (1) does not issue 



89. Cavities of the nose ? Obstruction of the passage of air through them ? 

 40. The special nerve of smell ? Its location ? 



