28 



SPECIAL SENSES. 



FIG. 1. 



tory bulb. This is grayish in color, excessively soft, and con- 

 tains the ordinary ganglionic elements. From the olfactory 

 bulb, from fifteen to eighteen nervous filaments are given off, 

 which pass through the foramina in the cribriform plate of 

 the ethmoid. These filaments are composed entirely of nerve- 

 fibres and are quite resisting, owing to fibrous elements pro- 

 longed from the dura mater. It is strictly proper, perhaps, to 

 regard these as the true olfactory nerves, the cord leading from 

 the olfactory bulb to the cerebrum being more properly a com- 

 missure. Having passed through 

 the cribriform plate, the olfac- 

 tory nerves are distributed to the 

 olfactory membrane in three 

 groups ; an inner group, distrib- 

 uted to the mucous membrane of 

 the upper third of the septum ; 

 a middle group, to the upper por- 

 tion of the nasal fossae ; and an 

 outer group, to the mucous mem- 

 brane covering the superior and 

 middle turbinated bones and a 

 portion of the ethmoid. 



The mode of termination of 

 i. From the frog.-o, epithelial cells of the the olf actory nerves differs from 



olfactory region ; b, olfactory cells. 2. , / , i T 



Small branch of the olfactory nerve of that OI the Ordinary 

 the frog, separating at one end into a 

 brush of varicose fibrils. 3. Olfactory 

 cell of the sheep. Magnified 350 diame- 

 ters. (K6LLIKER, Handbueh der Ge- 



i 



icebdehre, Leipzig, 186T, S. 743.) 



nerves, and is peculiar and char- 

 acteristic, as it is in the other 

 organs of special sense. Accord- 

 ing to the observations of Eckhard and Schultze, confirmed 

 by Kolliker, 1 the olfactory mucous membrane contains pecul- 

 iar terminal nerve-cells, called the olfactory cells, which are 

 placed between the cells of epithelium. These are long, deli- 

 cate, spindle-shaped structures, varicose, each one containing 

 a clear, round nucleus. The appearance of these, which are 

 considered as the true olfactory organs, is represented in Fig. 



1 KOLLIKER, Handbueh der Gewebelehre, Leipzig, 1867, S. 743. 



