398 



HISTOLOGY. 



each olfactory cell sends a slender cylindrical process towards the surface, 

 where it terminates in small hairs. Basally the olfactory cells pass directly 

 into the axis cylinders of the olfactory nerves (Fig. 449). Thus they are 

 ganglion cells, their basal processes being neuraxons. Cells intermediate 

 between the olfactory and sustentacular forms may be found. At the free 

 surface of the olfactory epithelium there are terminal bars, and small 

 masses of mucus sometimes suggesting cilia. The mucus is the product 

 of the sustentacular cells. Near the tunica propria there is a network of 

 so-called "basal cells" (Fig. 450). 



The tunica propria is a network of coarse fibrous tissue and fine 



Excretory duct. 



Wandering cell. Mucus. 



A 



Pigment granules. 



Oval nucleus of a 



sustentacular cell. 



;. Round nucleus of 



an olfactory cell. 





' *'' Sections of olfactory glands. 



Dilated duct. Mucus. 



FIG. 450. VERTICAL SECTION THROUGH THE OLFACTORY REGION OF AN ADULT. X 400 



elastic fibers associated with many connective tissue cells. In some animals 

 (for example, the cat) it forms a structureless membrane next to the epi- 

 thelium. It surrounds the numerous olfactory glands [Bowman's glands]. 

 In man these are branched cavities consisting of excretory ducts extending 

 through the epithelium, and of gland bodies beneath. Oblique sections 

 of the ducts have been mistaken for "olfactory buds." The glands in man 

 appear to be serous but they sometimes contain mucus in small quantity. 

 They are found not only in the olfactory region but also in the adjoining 

 part of the respiratory region. 



