CHAPTER XVI. 

 SENSATIONS OF TASTE AND SMELL. 



The sense of taste is mediated by nerve fibers distributed to 

 parts of the buccal cavity and particularly to parts of the tongue. 

 The most sensitive regions are the tip, the borders, and the posterior 

 portion of the dorsum of the tongue in the region of the circum- 

 vallate papillae. Taste buds and a sense of taste are described also 

 for the soft palate, the epiglottis, and even for the larynx. The 

 sense is not present uniformly over the entire dorsum of the tongue. 

 On the contrary, it has an irregular, punctiform distribution over 

 most of this region with the exception of the parts mentioned above. 



The Nerves of Taste. The anterior two-thirds of the tongue 

 are supplied with sensory fibers from the lingual nerve, a branch 

 of the inferior maxillary division of the fifth nerve, and the posterior 

 third from the glossopharyngeal. The taste fibers for these regions, 

 therefore, are supplied immediately through these nerves. It has 

 been shown, moreover, that the taste fibers carried in the lingual 

 are brought to it through the chorda tympani nerve, which arises 

 from the seventh cranial nerve and joins the lingual soon after 

 emerging from the tympanic cavity of the ear. There has been 

 much discussion as to the origin of these taste fibers from the brain. 

 At first sight it would seem that the fibers for the posterior third 

 of the tongue must have their origin from the brain in the glosso- 

 pharyngeal and those for the anterior two-thirds in the sensory 

 portion of the facial. Many surgeons have reported, however, that 

 complete extirpation of the Gasserian ganglion of the fifth nerve 

 is followed by complete loss of taste in the corresponding side of 

 the tongue, and others have described a loss of taste for the anterior 

 two-thirds following a similar operation. Some authors have 

 asserted, therefore, that all the taste fibers originate or rather end 

 in the sensory nucleus of the fifth, while others believe that the 

 fibers running in the chorda tympani, at least, take their origin in 

 the fifth nerve. It is supposed by these authors that the fibers 

 reach the Gasserian ganglion by a circuitous route, as is indicated 

 in the diagram given in Fig. 113. Those that run in the lingual 

 and chorda tympani nerves are assumed to pass to the ganglion 

 by way of the great superficial petrosal and Vidian nerves and 

 MeckeFs ganglion, while those that are contained in the glosso- 



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