Olfactory Apparatus in Dog, Cat and Man 33 



of his preparations. The olfactory fibers unite into thick bundles, but, 

 according to Van Gehuchten, the individual fibers do not vary in size 

 during their entire length. 



They are rarely varicose; the varicosity is probably due to an incom- 

 plete reduction of the stain. At the base of the epithelium the fibers 

 nuiy turn abruptly or may pass to the olfactory cell directly in a more 

 or less undulating course. The olfactory cell is bipolar, its peripheral 

 end is the longer and reaches the free surface, in some cases where there 

 is no deposit of silver, ending by a cilia-like projection as described by 

 Eanvier for the frog. The central process may be followed for some 

 distance in the connective tissue. Van Gehuchten concludes thus: by 

 methylene blue and by the Golgi method it has been proven that there 

 is a direct continuity of the olfactory fiber and the bipolar cell. There 

 is no plexus, as thought by Exner and Eanvier, no free intraepithelial 

 terminations, nor a connection of the nerve fibers with the cylindrical 

 cells in the limiting zone, as described by Grassi and Castronovo. 



von Brunn, 1892, finds the membrana limitans and the olfactory 

 hairs; these are on a bud-like swelling of the olfactory cell. He is not 

 certain whether or not the enlargements are due to reagents. The 

 olfactory hairs come out of holes in the membrana limitans; this 

 limitans is comparable to the homogeneous border which is penetrated 

 by cilia or ciliated cells, and he considers it comparable to a cuticular 

 border. 



He has seen the nerves join the olfactory cells and seen them join with 

 other threads, but has never seen free endings which were olfactory 

 fibers. He has seen fibers on the border of the olfactory and ciliated 

 epithelium which pass up into the epithelium, but these did not join 

 with any cell and were therefore free ending fibers. 



Betzius, 1892, worked on mouse, cat, dog and rabbit, using the rapid 

 Golgi method. He found two kinds of cells: the supporting cells and 

 the olfactory cells. The supporting cells had a nucleus in the outer 

 third of the cell body. The inner part of the cells had two, three or 

 more wing-like processes which reached to the inner surface of the 

 epithelium. These did not form a fiber. Between these supporting 

 cells were found the olfactory cells. They were bipolar; the cell body 

 was oval or spindle shape with two processes. The outer, thicker 

 process passed to the surface between the supporting cells and bore 

 cilia-like hairs. The inner one was much finer and often varicose. 

 There were several layers of cells, so that the processes were of varying 



