SENSE OF SMELL. 



299 



Olfactory Bulb 



Olfactory Nerves. 



Branches of 

 Fifth Nerve 



Turbinated Bones : 



ences the respiratory process. The presence of odors influ- 

 ences both the amplitude and the number of the respiratory 

 movements. Thus the smell of wintergreen notably increases 

 the respiratory work, next comes ylang-ylang, and last rose- 

 mary. The breathing of a fine odor is therefore not only a 

 pleasure, but it increases the amplitude of the respiratory 

 movements. Just as taste and flavor influence nutrition by 

 affecting the digestive process, and as the sight of agreeable 

 or beautiful 

 objects and 

 the hearing 

 of melodious 

 and harmo- 

 nious sounds 

 react on the 

 body an d 

 help physio- 

 logical well-being, so the 

 odors of the country, or 

 even those of the per- 

 fumer, play a beneficent 

 role in the economy of 

 life." JVFKENDRICK 

 and SNODGRASS. 



In quiet breathing the air passes along the lower air pas- 

 sages just above the hard palate. The true olfactory passages 

 are higher, but still in communication with this lower pas- 

 sage. When we wish to test the quality of the air, we sniff, 

 that is, make a sudden inspiration by jerking the diaphragm 

 down, and air from the outside then rushes into these upper 

 nasal passages, over the walls of which the nerves of smell, 

 the Olfactory Nerves, are spread in the mucous membrane. 

 The sudden rush of air against this membrane seems to aid 



Fig. 88. Nerves of the Outer Wall of the 

 Nasal Cavity. 



