CHAPTER II. 



ANATOMY OF THE OLFACTORY ORGAN. 



Contents. 1. Nasal Cavities in Man. 2. Nasal Mem- 

 branes. 3. Olfactory Epithelium. 4. Intermediate Zone. 

 5. Polymorphic Cells. 6. Sense Buds. 7. Free-nerve 

 Endings. 8. Development of Olfactory Nerve. 9. Com- 

 parative Anatomy of Olfactory Organs. 10. Bibliography. 



1. NASAL Cavities in Man. In man the olfactory 

 organs are paired and are situated one in each nasal 

 cavity. Each of these cavities possesses an external 

 opening, the anterior naris, and an internal one, the 

 posterior naris or choana, which communicates with the 

 pharynx. (Fig. 1). The two nasal cavities are separated 

 by the nasal septum, a partly bony, partly cartilaginous 

 wall, which forms a smooth median partition between 

 them. The lateral walls of these cavities are thrown into 

 a series of more or less horizontal folds, the nasal conchas. 

 These are commonly three in number for each cavity 

 though in some instances only two are present and in 

 others a fourth, fifth or even a sixth can be discerned. 

 Of the three conchae usually present the most ventral one, 

 the inferior concha, is the largest and extends through 

 much of the length of the cavity in a direction approxi- 

 mately parallel to its floor. Immediately above the inferior 

 concha is the somewhat smaller middle concha which 

 is followed by the still smaller superior concha. When 

 only two conchae are present, they are the inferior and the 



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