230 



THE KESPIKATORY SYSTEM 



Frequently they send a short process between the branched ends 

 of the sustentacular cells. 



Many small nerve trunks occur in the tunica propria. The 

 great majority of these are non-medullated and are formed by the 

 central processes of the olfactory cells. Several of the smaller 

 superficial fibre bundles unite in the deeper part of the tunica 

 propria to form one of the small olfactory nerves. A few medul- 

 lated fibres, derived from the trigeminus, are also found in the 

 tunica propria; they distribute their terminal branches to the 



? st 



Jfe* 



FIG. 195. THE OLFACTORY MUCOUS MEMBRANE. 



a, duct; 5, basal cells; c, cuticular border with olfactory cilia; , nuclei of the sus- 

 tentacular cells; k', nuclei of the olfactory cells; r, layer of olfactory cells; s, corium, 

 containing connective tissue cells and nerve fibres; st, sustentacular cells, x 465. 

 (After Kolliker.) 



blood vessels, and, by fine sensory filaments which end between 

 the epithelial cells, to the neuro-epithelial layer. 



The blood vessels cf the olfactory mucous membrane are abun- 

 dant. Their capillary plexuses form several layers in the tunica 

 propria, and their veins mostly empty, through the ethmoidal 

 veins, into the superior longitudinal sinus a most significant fact. 

 On the other hand the veins of the respiratory region return their 

 blood to the internal maxillary vein, while some of those of the 



