550 THE CRANIAL NERVES. 



panum near the inner surface of the membrana tympani, curves down- 

 ward and forward, and joins the descending portion of the lingual nerve. 

 It is certain that some of its fibres again leave the lingual nerve at the 

 situation of the subm axillary ganglion, to reach this ganglion and the 

 tissue of the submaxillary gland ; and it is also certain that some of 

 them continue onward with the lingual nerve, and accompany it to its 

 distribution in the tongue. 



The most positive knowledge in our possession with regard to the 

 physiological character of the chorda tympani is that it is distinctly a 

 motor nerve, influencing the acts of circulation and secretion. This 

 results from the numerous experiments of Bernard 1 on the dog and cat, 

 which show that, in these animals, galvanization of the chorda tympani 

 increases at the same time the activity of the circulation and the secre- 

 tion of saliva in the submaxillary gland. The gland, with its excretory 

 duct and nervous connections, is exposed in the living animal. It is then 

 seen that the introduction of vinegar into the fauces causes, by reflex 

 action, an increased current of blood through the vessels of the gland, 

 and excites an abundant flow of submaxillary saliva. But if the chorda 

 tympani be tied or cut across, the action above described no longer takes 

 place, and the gland remains inexcitable under the influence of a sapid 

 substance introduced into the fauces. On the other hand, if the peri- 

 pheral extremity of the nerve be galvanized, this stimulus excites the 

 circulation and secretion as before ; and the same effect is produced by 

 stimulating, either the lingual nerve itself, or the filament which it sends 

 to the submaxillary gland. Finally, while section of the chorda tym- 

 pani in the cavity of the tympanum, or evulsion of the facial nerve from 

 the aqueduct of Fallopius, will arrest the secretive activity of the sub- 

 maxillary gland, section of the facial at the stylomastoid foramen does 

 not have this effect, but only paralyzes the muscles of the face. A dif- 

 ference accordingly exists, in the effects produced by injury of the facial 

 nerve, according to its location, within the aqueduct of Fallopius or out- 

 side of this canal. If the lesion be external, there is simple paralysis of 

 the facial muscles. If it be internal, there is also a diminished activity 

 of circulation and secretion in the submaxillary gland. 



Another symptom sometimes observed in deep-seated lesions of the 

 facial nerve, which is also dependent on injury of the chorda tympani, 

 is a diminution or disturbance of the sense of taste in the tip and sur- 

 face of the tongue. In this affection, the taste is not absolutely abol- 

 ished, but is diminished in acuteness, and especially in promptitude. 

 In a person presenting this difficulty, or in an animal after division of 

 the chorda tympani, if a bitter substance be placed alternately upon 

 the two sides of the tongue, it is perceived almost immediately upon 

 the sound side, but only after a considerable interval on the side of the 



1 Systeme Nerveux. Paris, 1858, tome ii. pp. 150-157. Liquides de TOrganisme 

 Paris, 1859, tome i. pp. 310-315. 



