484 



HISTOLOGY 



cat, "sensory cells apparently identical with those of the olfactory 

 mucosa." In man sensory cells are said to be lacking in the adult and 

 in embryos older than five months. 



In the regio olfactoria the mucosa includes a tunica propria and an 



olfactory epithelium. The latter consists of 

 sustentacular cells and olfactory cells. The 

 superficial halves of the sustentacular cells 

 are cylindrical, and contain yellowish pig- 

 ment, together with small mucoid granules 

 often arranged in vertical rows (Fig. 490) . 

 The more slender lower halves have den- 

 tate or notched borders, and branched 

 basal ends which unite with those of neigh- 

 boring cells, thus forming a protoplasmic 

 network. Their nuclei, generally oval, are 

 in one plane and in vertical sections they 

 form a narrow "zone of oval nuclei" 

 (Fig. 491). The olfactory cells generally 



have round nuclei containing nucleoli. They occur at different levels 

 and so form a broad "zone of round nuclei." From the protoplasm 



FIG. 490. ISOLATED CELLS OF THE OL- 

 FACTORY MUCOSA OF A RABBIT. 

 X 560. 



st, Supporting cells; s, extruded mucus 

 resembling cilia; I, olfactory cells, from 

 r' the lower process has been torn off; f, 

 ciliated cell; b, cells of olfactory glands. 



Excretory duct 



Wandering cell. Mucus. 



\ 



rT.y _ Pigment 



granules. 



Oval nucleus of 



a sustentacular 



cell. 



Round nucleus 

 of an olfactory 

 cell. 

 Basal celL 



Nerve. 



tf 



Sections of olfactory glands. 



FIG. 491. VERTICAL SECTION THROUGH THE OLFACTORY REGION OF AN ADULT. X 400. 



Dilated duct. Mucus. 



which is gathered immediately about the nucleus, each olfactory cell 

 sends a slender cylindrical process toward the surface, where it ter- 



