THE SENSE OF SMELL. 



633 



thelium not provided with cilia ; and interspersed with these 

 are peculiar fusiform cells with fine processes, called olfactory 

 cells. They are supposed to have some connection with the 

 terminal filaments of Fig. 170.* 



the olfactory nerve. The 

 lower, or respiratory 

 part, as it is called, of 

 the nasal fossae is lined 

 by cylindrical ciliated 

 epithelium, except in 

 the region of the nos- 

 trils, where it is squa- 

 mous. 



In all the distribu- 

 tion, the branches of 

 the olfactory nerves re- 

 tain much of the same 

 soft and greyish tex- 

 ture which distinguishes 

 their trunks (as the olfactory lobes of the brain are called) 

 within the cranium. Their individual filaments, also, are 

 peculiar, more resembling those of the sympathetic nerve 

 than the filaments of the other cerebral nerves do, con- 

 taining no outer white substance, and being finely granular 

 and nucleated. The branches are distributed principally 

 in close plexuses ; but the mode of termination of the fila- 

 ments is not yet satisfactorily determined. 



* Fig. 170. Nerves of the outer walls of the nasal fossae (from Sappey 

 after Hirschfeld and Leveille). f. I, network of the branches of the 

 olfactory nerve, descending upon the region of the superior and middle 

 turbinated bones ; 2, external twig of the ethmoidal branch of the 

 nasal nerve ; 3, spheno-palatine ganglion ; 4, ramification of the anterior 

 palatine nerves ; 5, posterior, and 6, middle divisions of the palatine 

 nerves; 7, branch to the region of the inferior turbinated bone; 8, 

 branch to the region of the superior and middle turbinated bones ; 9, 

 naso-palatine branch to the septum cut short (after Sharpey). 



