128 PHYSIOLOGY AND TEMPERANCE. 



3. The Sense of Smell. The outward shape of the 

 most conspicuous feature of the face needs no description. 

 The frame-work of the nose consists of bone and cartilage. 

 Fourteen bones enter into the formation of this organ. Four 

 plates of bone are so placed as to form a strong arch, the 

 bridge of the nose, capable of resisting considerable outside 

 force. Joined to the plates of bone, on either side, are plates 

 of cartilage to form the nostrils. The chamber thus formed 



OLFACTORY NERVE 



Y 



BRANCHES Of 

 OLFACTORY NERVF 



FIG. 38. Sectional view of the Nose. 



is large and is divided by a vertical wall into two halves. 

 The floor of the nasal cavity constitutes the roof of the mouth. 

 At the back part of the roof of the nose is a very thin plate 

 of bone, on which rests a portion of the brain. This bone is 

 pierced by numerous little holes, giving it the appearance of 

 a sieve. The olfactory nerve, or nerve of smell, lies on this 

 bone, and gives off, from its bulb-like end, quantities of little 

 filaments, which reach the nasal cavity through these holes 

 and spread out on the mucous membrane. 



