670 



THE NOSE. 



Fi?. 485. 



pnrface are prolonged at their deep extremities into a process generally 

 somewhat thickened towards its deeper end, which usually includes a 

 number of fatty granules ; and from this thickened part branches pro- 

 ceed, which are stated byExner and Martin to communicate with those 

 of neighbouring cells, so as to form a communicating network through- 

 out the extent of the membrane, underneath the epithelium. Between 

 and amongst these branching central ends of the columnar cells there 

 are a large number of peculiar spindle-shaped cells (fig. 485, h), each 

 consisting of a large, clear nucleus -surrounded by a relatively small 

 amount of granular protoplasm. From each cell proceeds a superficial 

 and a deep process. The superficial process (c) is a cylindrical or shghtly 

 tapering thread passing directly to the surface, and terminating abruptly 



at the same level as the epithelial 

 cells between wdiich it lies : the 

 deep process (^/) is more sleudei', and 

 passes vertically inwards. This last 

 frequently presents a beaded ap- 

 pearance similar to that observed 

 in fine nerve-filaments, and con- 

 sidered to be of a similar accidental 

 origin. These cells were termed by 

 Max Schultze, their discoverer, olfac- 

 iory cells, to distinguish them from 

 the columnar epithelium cells above 

 described, than which they are much 

 more numerous, and which they entirely 

 surround with their fine rod-like peri- 

 pheral processes. It is probable that 

 their fine varicose central processes are 

 directly continuous with the fibrils of 

 the olfactory nerve, but the continuity 

 lias never been actually observed. 

 The nucleated bodies of the olfactory 

 cells are several rows deep, and form a 

 layer of considerable thickness beneath 

 the columnar cells. 



Fig. 485. — Cells and Terminal 

 Nkrve-fibres of the Olfactory 

 Reoion (from Frey after Schultze). 

 Highly magnified. 



1, from the frog ; 2, from man ; 

 a, epithelial cell, extending deeply 

 into a ramified process ; h, olfactory 

 cells ; c, their peripheral rods ; e, 

 their extremities, seen in 1 to be 

 prolonged into fine hairs ; d, their 

 central filaments ; 3, olfactory nerve- 

 fibres from the dog ; a, the division 

 into fine fibrillte. 



be met with between the two, 

 a common network, to which, 



The superficial process of the olfactory 

 cell was observed by Schultze to be sur- 

 mounted by a short, stiff projection (fig. 

 485, 2f)j ^^^ l^^s been so described by 

 others; but it is now agreed that this 

 appearance results from the coagulation of 

 albuminous matter escaped from the interior 

 of the process. Long and fine hair-lUie pro- 

 cesses do, however, exist on the olfactory 

 membranes of amphibia, reptiles, and birds 

 (fig. 485. Ic')- b^t they have not been observed 

 in mammals. 



A doubt has been thrown by Exner upon 



the definiteness of the distinction between 



the epithelial and the olfactory cells of this 



region : he states that every transition may 



and that the central processes of both end in 



moreover, the nerve fibrils are distributed. 



