1414 



II I'M AN ANATOMY. 



FIG. 1177. 



respiratory mucous membrane, tongues or even islands of the latter projecting into 

 or being surrounded by the former. Upon the evidence derived from careful dissection 

 of the olfactory mucous membrane, however, it is difficult to avoid the conclusion 



that Brunn's areas are too limited, as nerve-fila- 

 ments clearly attached to the olfactory bulb are 

 usually traceable onto the upper part of the middle 

 turbinate bone. In fresh preparations the olfactory 

 area usually, but not always, can be approximately 

 mapped out by the yellowish hue, lighter or 

 darker, that distinguishes it from the respiratory 

 region in which the mucous membrane exhibits 

 a rosy tint. 



The epithelium contains two chief con- 

 stituents the supporting and the olfactory cells. 

 The supporting cells are tall cylindrical elements, 

 about .06 mm. in height, that extend the entire 

 thickness of the epithelium. Their outer and 

 broader ends are of uniform width and contain 

 the oval nuclei which, lying approximately at 

 the same line and staining readily, form a 

 deeply colored and conspicuous nuclear stra- 

 tum at some distance beneath the free margin. 

 Between the latter and the row of nuclei, the 

 epithelium presents a clear zone devoid of 

 nuclei. The inner part of the supporting cells 

 is thinner and irregular in contour and often 

 terminates by splitting into two or more basal processes that rest upon the tunica 

 propria. Between these ends lie smaller pyramidal elements, the basal cells, that 



FIG. 1178. 



Right nasal fossa, septum (s) has been 

 partially separated and turned upward ; dark 

 field shows olfactory area on lateral and mesial 

 walls of fossa, as mapped out by Brunn.. 



oT,:: ce, ls 



Bundle of 



olfactory nerves 



Section of olfactory mucous membrane; epithelium displays outer nuclei-free and nuclear layers formed by 

 supporting; cells and broad stratum containing nuclei of olfactory cells. X 300. 



probably represent younger and supplementary forms of the sustentacular cells. 

 Tin- granular protoplasm of the basal processes often contains pigment particles. 



The olfactory cells, the perceptive elements receiving the smell-stimuli, con- 

 .si>t of a fusiform body, lodging a spherical nucleus enclosed by a thin cn\-elope of 

 cytoplasm, and two attenuated processes, a peripheral and a central. The olfactory 

 cells are in fact sensory neurones that have retained their primitive position within 

 the surface epithelium, as in many invertebrates, instead of receding, as is usual in 



