Bawden, Nose and Jacob son's Organ. 137 



IV. Innervation and Histology of the Epithelium of the Nose 

 and Jacobsoris Organ. 



Histology of the Epithelium. — The olfactory epithelium is 

 usually the simplest form of neuro-epithelium found in animals. 



The single olfactory cells which are the first indications of a 

 specialized sense-organ for smell, are the phylogenetic deriva- 

 tives of the olfactory buds seen in the olfactory crypts in the 

 adult higher forms. In almost all cases the olfactory epithelium 

 is more highly developed on the side toward the brain, the 

 thinner walls of neuro-epithelium lying upon the ventral and lat- 

 eral surfaces. It is often lobed or corrugated also on the side 

 nearest the olfactory bulb, where then erves enter. See Fig. 3, 

 cor, Plate VII. 



The uncertainty formerly existing in the minds of many 

 investigators as to the exact nature of the termini of the olfac- 

 tory nerve in the nasal cavity and in Jacobson's organ seems 

 now to be quite satisfactorily removed. The concurrent testi- 

 mony of so skillful investigators as Cajal, Van Gehuchten, Len- 

 hossek, Brunn and Retzius, leaves but little doubt that the so- 

 called olfactory cells of the olfactory epithelium and of Jacob- 

 son's organ are real nerve cells and that there is actual nervous 

 continuity between the cilia at one pole and the fibre of the 

 olfactory nerve springing from the other pole of these cells. 

 Preparations recently made in our laboratory both by the Golgi 

 method and by the hematoxylin process (and figured in Plate 

 XIX, Figs. 1, 2, and 3; plate XX, Fig. 3, Journal of Compara- 

 tive Neurology, September, 1893) prove conclusively, if ad- 

 ditional proof were necessary, that the fibres of the olfactory 

 nerve as they pass into the olfactory tuber break up into ter- 

 minal brushes ( "end-baumchen" ) in the glomerules without 

 coming into relation with any cells at this end of their course. 

 In accordance, then, with the current morphological ideas of 

 nervous structure, the peripheral neuron of the olfactory system 

 would consist of the olfactory ganglion cell in the nasal mem- 

 brane, its axis-cylinder process which forms one of the constit- 

 uent parts of the olfactory nerve, and its terminal brush in the 



