CHAPTER XVII. 



THE SPECIAL SENSES. 



The special senses are located in the nose, eye, 

 tongue, skin and ear. 



THE NOSE. 



The mucous membrane of the nose is divided into 

 two tracts, the respiratory and the olfactory. The ol- 

 factory is the tract that furnishes the cell in which the 

 nerves end that carry the sensation of odor to the cen- 

 ter of olfaction or smell. It consists of two layers of 

 epithelial cells. The cells that receive the sensation 

 are very long and nucleated. The cells in which the 

 sensation is generated are placed beneath a layer of 

 tall, columnar cells. The nerves are of both kinds. 

 The special nerves communicate with the olfactory 

 center. The sensory nerves do not come in contact 

 with the olfactory cells. They are derived from the 

 trifacial, while the others are derived from the ol- 

 factory nerve. The blood vessels are found in the 

 sub-epithelial layer ending in capillaries. The lym- 

 phatics are numerous. 



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