SENSE OF TASTE. 405 



lary gland, for which reason Cl. Bernard has suggested that 

 this gland should be considered as essentially connected with 

 the, functions of gustation. 



The nerves of taste are the lingual and the glosso-pharyn- 

 geal nerves. The lingual, which is a branch of the trigeminus, 

 extends to the posterior part of the tongue, imparting to it 

 general and tactile sensibility, as well as taste. The glosso- 

 pharyngeal nerve extends to the base, and regulates the 

 gustatory sensibility of the large papillae (Fig. 104). Jt 

 is this nerve, chiefly, which transmits the impressions made 

 by bitter substances : for this reason it has been called, too 

 exclusively, as it would seem, the nauseant nerve. The lin- 

 gual and glosso-pharyngeal nerves thus govern equally the 

 sense of taste, and both possess fibres of general sensibility , 

 but that the fibres of feeling or general sensibility are quite dis- 

 tinct from the fibres of taste is apparently proved by the fact 

 that one of these senses (taste) may entirely cease, while the 

 general sensibility and power of sensation in the tongue con- 

 tinue unimpaired. 



The question has arisen whether it would not be possible to 

 separate the fibres of taste from the fibres of touch in the glosso- 

 pharyngeal and the lingual nerves. No method is as yet known by 

 which the former may be separated, but the study of paralysis of 

 the facial nerve in the posterior part of the tongue, the region 

 innervated by the lingual nerve, this paralysis being accompanied 

 by tho loss of taste, has led to the belief that the solution may 

 possibly be found by studying the chorda tympani, a small nerve 

 thread which, beginning in the facial nerve, traverses the middle 

 ear, and joins the lingual nerve at the level of the pterygoid 

 muscles (Figs. 105 and 10G). 



The study of the functions of the chorda tympani is one of the 

 most delicate questions. We have already spoken of the office of this 

 nerve or cord in reference to the secretion of the saliva. We were 

 then seeking to discover whether all the fibres of this nerve cease 

 at the level of tho submaxillary gland, or whether any of them go 

 beyond this, and extend to the tongue. In spite of numerous con- 

 tradictory experiments, physiologists now nearly all agree in the 

 opinion that the chorda tympani does extend to the tongue. 

 Vulpian and Prevost have constantly found degenerated nerve 

 fibres in the terminal branches of the lingual nerve, after the 

 chorda tympani had been destroyed, either by being cut in the ear, 

 or by the removal of the facial nerve : these degenerated fibres can 

 only arise from the chorda tympani. 



The next inquiry to be made was whether the chorda tympani is 

 united to the tongue as a motor or as a sensory nerve. The latter 

 function is now assigned to it by some physiologists, especially 

 Lussuiia and Schiff , both of whom maintain that the chorda tympaui 



