638 SPECIAL SENSES 



proper gradation of gustatory and odorous impressions is illustrated in 

 the modern cuisine, which aims at an artistic combination and succes- 

 sion of dishes and wines, so that the agreeable sensations are prolonged 

 to the utmost limit. This may often be regarded as a violation of 

 strictly hygienic principles, but it none the less exemplifies the cultiva- 

 tion of the sense of taste. 



Nerves of Taste. Two nerves, the chorda tympani and the glosso- 

 pharyngeal, are endowed with the sense of taste. These nerves are 

 distributed to distinct portions of the gustatory organ. The chorda 

 tympani has already been referred to as one of the branches of the 

 facial ; the glosso-pharyngeal has not yet been described. 



Chorda Tympani. In the description already given of the facial, 

 the chorda tympani is spoken of as the fourth branch. It passes 

 through the tympanum, between the ossicles of the ear, and joins the 

 inferior maxillary division of the fifth at an acute angle, between the 

 two pterygoid muscles, becoming so closely united with it that it can 

 not be followed farther by dissection. The filaments of this branch 

 probably originate from the intermediary nerve of Wrisberg, which 

 some anatomists describe as arising from the glosso-pharyngeal. The 

 course of the filaments of the chorda tympani, after this nerve has 

 joined the fifth, is shown by the effect on the sense of taste and the 

 alteration of the nerve-fibres following its division ; and observations on 

 the sense of taste show that this nerve is distributed to the anterior 

 two-thirds of the tongue. The general properties of the chorda tym- 

 pani have been ascertained only by observations made after its paralysis 

 or division. All experiments in which a stimulus has been applied 

 directly to the nerve in living animals have been negative in their 

 results. 



In paralysis of the facial in which the lesion affects the root so deeply 

 as to involve the chorda tympani, there is loss of taste in the anterior 

 two-thirds of the tongue, general sensibility being unaffected ; and many 

 cases illustrating this fact have been recorded. Aside from cases of 

 paralysis of the facial with impairment of taste, in which the general 

 sensibility of the tongue is intact, instances are on record of affections 

 of the fifth pair, in which the tongue was insensible to ordinary impres- 

 sions, the sense of taste remaining. 



Passing from the consideration of pathological facts to experiments 

 on living animals, the results are equally satisfactory. Although it is 

 somewhat difficult to observe impairment of taste in animals, experi- 

 menters have succeeded in training dogs and cats so as to observe the 

 effects of colocynth and various sapid substances applied to the tongue. 

 In a number of experiments of this kind, it has been observed that after 



