THE OLFACTORY APPARATUS 695 



The nose is not entirely an organ for the seat of smell. In fact the nasal 

 cavities are divided into three districts called, respectively : i , Regio vestibularis 

 which is the entrance to the cavity. It is lined with a mucous membrane very 

 closely resembling the skin, and guarded by hairs and by sebaceous glands. 

 2, Regio respiratorid, which includes the lower and middle meatus of the 

 nose. It is covered with mucous membrane of stratified columnar ciliated 

 epithelium. The mucosa is thick and consists of fibrous connective tissue; 

 it contains a certain number of tubular mucous and serous glands. 3, Regio 



FIG. 427. Nerves of the Outer Walls of the Nasal Fossae, i, Network of the branches 

 of the olfactory nerve, descending upon the region of the superior and middle turbinated 

 bones; 2, external twig of the ethmoidal branch of the nasal nerves; 3, spheno-palatine 

 ganglion; 4, ramification of the anterior palatine nerves; 5, posterior, and 6, middle divisions 

 of the palatine nerves; 7, branch to the region of the inferior turbinated bone; 8, branch to 

 the region of the superior and middle turbinated bones; 9, naso-palatine branch to the 

 septum cut short. (From Sappey, after Hirschfeld and Leveille.) 



olfactoria. This includes the anterior two-thirds of the superior meatus, the 

 middle meatus, and the upper half of the septum nasi, figures 427 and 428. 

 It is of a yellowish color. It consists of a thicker mucous membrane than 

 in 2, made up of loose, areolar connective tissue covered by epithelium of a 

 special variety, resting upon a basement membrane. The cells of the epithe- 

 lium are of two principal kinds: 0, columnar epithelial cells whose function 

 is to support b, the bipolar olfactory cells. The epithelial cells are prismatic 

 in shape and have upon their surfaces facets into which the olfactory cells 

 fit themselves, figure 428, e. They are thus analogous to the cells of Miiller 

 of the retina. The olfactory cells have an oblong or fusiform shape, which 

 is mainly determined by the large nucleus. The thin protoplasmic body has 

 two processes, an external and an internal. The external is large and passes 

 up to the free surface, to end in a small bunch of fibrils that are not vibratile. 

 The internal process is very fine, often varicose, and passes through the 



