XVII 



THE SENSE ORGANS 



323 



are connected usually by means of branching processes, 

 with the ramifications of the supplying nerve. 



The Olfactory Organs. — The seat of smell is in the nasal 

 cavity, the walls of which are supplied with the olfactory 



d b 



\^ Plex. subepithel. 



Plex. subbas, 



Fig. 87. — Section through a fungilorm papilla. A bundle of nerve fibers 

 enters the papilla from below, breaking up into first the subbasal plexus, 

 and second the subepithelial plexus around the bases of the cells of 

 columnar epithelium. The latter plexus forms connections with the 

 branches of the sensory cells, a, free nerve endings ; b, c, d, nerve cells ; 

 ^,/ cells connected with the subepithelial plexus. (From Gaupp, after 

 Niemack.) 



nerves. The nasal cavity is lined by a mucous membrane 

 which is composed of a connective tissue substratum and 

 an outer layer of olfactory epithelium. In the regions to 

 which the olfactory nerves are distributed the epithelium 

 consists of three kinds of cells : (i) interstitial cells, which 



