THE ORGANS OF SENSE. 



239 



(as a rule) non-ciliated epithelial mass finally covers the 

 olfactory region. 



Let us first examine this epi- 

 thelium. 



We here meet with two differ- 

 ent elements. Firstly (a), long 

 cylindrical cells (2 a). Their body 

 contains yellowish granules and, 

 in connection with the Bowman's 

 glands, causes the mentioned 

 color of our locality. The lank 

 non-ciliated cylinder sends down- 

 wards a thin process which 

 becomes divided. By the union 

 of such systems of processes a 

 regular horizontal net-work is 

 formed in the connective tissue 

 of the mucous membrane. 



The cells just described have 

 nothing at all to do with the 

 nerve termination. They are a 

 modified, but indifferent epithe- 

 lium. 



Between them, however, there 

 appears a second cell formation, 

 the terminal structure of the olfac- 

 tory nerve, the olfactory cell (b) ; 

 thus called, and with probability. 

 times more deeply situated, we meet with a spindle-shaped 

 cell body (1, 2, b). Below (1,2, d) the latter gives off an 

 exceedingly thin filamentous process. It presents, with cer- 

 tain treatment, small varicosities, like a primitive fibrilla of 

 the nerve fibre (p. 196). At the upper pole, our spindle 

 cell sends off a broader, smooth rod (1, 2, c), 0.0018 to 

 0.0009 mm - wide. Ascending between the epithelial cylin- 

 ders, it reaches the surface of the parts. 



In many animals, the terminal surface of the rod has 



Fir;. 194. — 1. Cells of the regio olfac- 

 toria of the frog ; a, an epithelial cell, 

 terminating below in a ramified process ; 

 b, olfactory cells with the descending fila- 

 ment ; d, the peripheral rod, c, and the 

 long vibratile cilia;, e ; ?, cells from the 

 same region of man. The references the 

 same, only sh'.rt projections, e, occur 

 (as artefacts I on the rods : 3, fibres of 

 the olfactory nerve from the dog ; at a 

 dividing into n.,i_ fibrillae. 



at least, it is at present 

 Sometimes higher, some- 



