THE SENSES. 



consists of two different kinds of elongated cells, both standing verti- 

 cally upon the mucous membrane, and closely adherent to each other by 

 their lateral surfaces. One portion are analogous in form to ordinary 

 nucleated columnar epithelium cells ; the remainder are very slender and 

 filamentous, except in their middle portion, at the situation of their oval 

 nucleus. The deeper portion of these cells, which is also more slender 

 than the rest, has been found to resemble the material of the nerve fibres 

 in its reaction with solutions of gold chloride ; but a direct continuity 

 of substance between the fibres and the cells has not been shown in an 

 unequivocal manner. 



There is no doubt that the nerve filaments given off from the olfac- 

 tory bulb are the special agents for communicating impressions of smell, 

 and that they are the only ones endowed with olfactory sensibility. 

 This follows from their exclusive and abundant distribution to the olfac- 

 tory portion of the nasal membrane, from their comparatively large 

 development in animals of acute smell, from the absence of this sense 

 in cases of congenital absence of the olfactory bulbs, and from its loss 

 in animals after their destruction (p. 515). So far as we can judge 

 from the results of experiment, they are not capable of receiving or 

 transmitting any other kind of sensibility than that excited by odor- 

 iferous substances. 



II. The second set of nerves distributed to the nasal passages con- 

 sists of the nasal branch of the fifth pair, and its ramifications (Fig. 

 188, 2). This nerve, after entering the cavity of the nose just in advance 

 of the cribriform plate of the ethmoid bone, sends its filaments mainly 

 to the mucous membrane covering the inferior turbinated bone and the 

 walls of the inferior meatus, which are thus supplied with general sen- 

 sibility, though they are destitute of the power of smell. JSome filaments 

 from this nerve, however, are also continued into the mucous membrane 

 of the olfactory region, where they run in proximity to those of the 

 olfactory nerves; and this region, according to the observations of 

 Babuchin, 1 possesses consequently a certain amount of general sensi- 

 bility, though much less than the remainder of the nasal passages. 



III. The third set are those derived from the spheno-palat ine gan- 

 glion of the sympathetic (Fig. 188, 3) which supply the mucous mem- 

 brane of the posterior part of the nasal passages and the muscles aiding 

 in the closure of the posterior nares. Finally, the muscles which regu- 

 late the expansion of the anterior nares are supplied by filaments of the 

 facial nerve. 



Necessary Conditions of the Sense of Smell In order to produce 



an olfactory impression, the emanations of the odoriferous body must 

 be drawn freely through the nasal passages. As the sense of smell is 

 situated only in the upper part of these passages, whenever an unusu- 

 ally faint or delicate odor is to be perceived, the air is forcibly directed 

 toward the superior turbinated bones, by a peculiar inspiratory move- 

 In Strieker's Manual of Histology, Buck's Edition. New York, 1872, p. 799. 



