622 



NERVOUS SYSTEM. 



canal, and before it has received any anastomosing branches from sensitive nerves, must 

 be to a certain extent unsatisfactory. All who have experimented upon the nerves know 

 that the pain and depression which attend so serious an operation as that of exposing 

 the roots of a nerve in the cranial cavity are sufficient to render it doubtful whether the 

 parts be in a condition to exhibit a slight degree of sensibility, which the nerves may 

 possess when perfectly normal. Magendie and Bernard, who have exposed the roots of 

 origin of the facial, state unreservedly that they are absolutely insensible ; but Longet 

 very justly remarks that the conditions under which such observations are made have 

 not been, in his hands, sufficiently favorable to admit of a rigorous conclusion upon this 

 point. The testimony of direct experimentation is in favor of the insensibility of the 

 facial at its origin. It is true that the intermediary nerve of Wrisberg has a certain ana- 

 tomical resemblance to the sensitive nerves, chiefly by virtue of its ganglioform enlarge- 

 ment ; but direct experiments are wanting to show that it is actually sensitive. In view 

 of this fact, it is impossible to reason conclusively from its anatomical characters alone. 



The most convenient way to consider the functions of the facial will be to take up 

 seriatim the properties and distribution of its different branches. 



Functions of the Branches of the Facial within the Aqueduct of Fallopius. The first 

 branch, the large petrosal, is the motor root of Meckel's ganglion. This will be referred 

 to again in connection with the sympathetic system. The second branch, the small petro- 

 sal, is one of the motor roots of the otic ganglion of the sympathetic. The third branch, 

 the tympanic, is distributed exclusively to the stapedius muscle. The seepnd and third 

 branches will be again considered in connection with the physiology of the internal ear. 

 The fourth branch, the chorda tympani, is so important that it demands special consid- 

 eration. The fifth branch is given off opposite the origin of the chorda tympani and 

 passes to the pneumogastric, to which nerve it probably supplies motor filaments. We 

 have already seen, in studying the properties of the roots of the facial, that, in this 

 branch, sensory filaments pass from the pneumogastric and constitute a part of the sen- 

 sory connections of the facial. 



Functions of the Chorda Tympani. This branch passes between the bones of the ear 

 and through the tympanic cavity to the lingual branch of the inferior maxillary division 



of the fifth, which it joins at an acute angle, 

 between the pterygoid muscles. It has 

 been a question whether this nerve be 

 simply enclosed in the sheath of the lingual 

 branch of the fifth or be so closely con- 

 nected with it that it cannot be traced to 

 a distinct distribution. Upon this point 

 we are disposed to adopt the opinion of 

 Sappey, who, as the result of minute dis- 

 sections, regards the union as complete, 

 " fibril to fibril." As regards the portion 

 of the facial which furnishes the filaments 

 of the chorda tympani, it is impossible to 

 determine anatomically whether these 

 come from the main root or from the in- 

 FIG. 202. Chorda-timpani nerve. (Hirschfeid.) termediary nerve of Wrisberg, as the fibres 



1, 2, 3, 4, facial nerve passing through the aquseductus Fal- / , i 



lopii; 5, gangiioform enlargement; 6, great petrosal of these roots are closely united before the 



nerve; 7, spheno-palatine ganglion; 8, small petrosal P >,orfla tvmnflni k O-IVPTI off 



nerve; 9, chorda tympani; 10, 11, 12, 13, various ua tyinpdni on. 



branches of the facial; 14, 14, 15, glosso-pharyngeal The Only questions that we propose to 



nerve. 



consider in this connection relate to the 



functions of the chorda tympani as a nerve of gustation, and as it influences the secretion 

 of the submaxillary gland. 



There can be no doubt with regard to the influence of the chorda tympani upon the 



