THE SENSES. 673 



the non-continuity of the neurons .was demonstrated (fig. 393). This 

 layer also contains small fusiform cells with branching dendrites that 

 extend outward to the glomeruli. Each has an axis-cylinder process 

 which passes inward to join the fibres of the internal olfactory nerves. 



3d. The layer of mitral cells contains large cells, some of them trian- 

 gular and some in the shape of a mitre. They have numerous dendrites, 

 one of which passes into a glomerule and then breaks up in a fine arbori- 

 zation. An axis-cylinder process (neuraxon) passes off from the inner 

 surface and is continued as an internal olfactory nerve-fibre. 



4th. The layer of granules and central fibres. This contains a 

 large number of very small nerve-cells, which are peculiar in that they 



, ?' i Nerves f the uter walls of the nasal fossas. 3-5. 1, 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 nerves; 3, spheno palatine ffanslion- 4' 

 ramification of the anterior palatine nerves; 5, posterior, and 6 midSle divisions of the a?atine 

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



naso-palatine branch to the septum &* 



have no axis-cylinder. Their dendrites extend chiefly into the layer 

 of mitral cells. They resemble the spongioblasts of the retina and prob- 

 ably have commissural functions. This layer has also some small star- 

 shaped cells whose dendrites end in the mitral cell-layer. Among these 

 cells run numerous fibres, chiefly from the mitral cells and the fusiform 

 cells of the glomerular layer. 



The general arrangement is shown in fig. 393. 



The sense of smell is derived exclusively through those parts of the 

 nasal cavities in which the olfactory nerves are distributed; the accessory 

 cavities or sinuses communicating with the nostrils seem to have no re- 

 lation to it. Air impregnated with the vapor of camphor was injected 

 43 



