38 NERVOUS SYSTEM. 



and others (mylo-hyoid and the anterior belly of the digas- 

 tric) depress the jaw, perhaps, also, to the stapedius and to 

 the internal muscle of the malleus; but these last-named 

 filaments appear to be mostly branches belonging to the facial, 

 as well as to the secretory, filaments, which go to the sub- 

 maxillary, sublingual (chorda tympani), and parotid glands. 

 ^ Summing up, it will be seen that the trifacial nerve essen- 

 tially presides over the sensibility of the three grand divisions 

 of the face (forehead, cheeks, and chin), whence the name 

 trigeminus or trifacial. 



^Facial Nerve (portio dura of the 7th pair). This is 

 essentially a centrifugal nerve (motory and secretory) ; the 

 secretory functions devolve apparently on the intermediary 

 nerve of Wrisberg (Cl. Bernard). The facial receives some 

 sensory anastomoses which proceed to it from the pneumo- 

 gastric and trifacial nerves. 



By its terminal branches this nerve presides over the 

 movements of all the cutaneous (peauciers) muscles of the 

 head, from the frontal to the occipital, comprising among 

 these the buccinator, and even to the cutaneous muscle of 

 the neck. Through its filaments, whose path is as compli- 

 cated as the windings of the aqueduct of Fallopius, whose 

 canal it follows, it presides over the secretion from the dif- 

 ferent salivary glands, the contraction of the muscles con- 

 cerned in the first intervals of deglutition (velum palati, 

 styloid muscles, posterior belly of the digastric, etc.), as well 

 as the contractions of the muscles of the middle ear (tensor 

 tympani, or musculus internus mallei, and stapedius). Lon- 

 get regards the branches given off to these last two muscles 

 as being the continuation of the intermediary of Wrisberg 

 which he names consequently motory tympanic nerve. 



By the above physiological notions, it is explained why 

 paralyses of the facial nerve, arising from superficial causes, 

 are characterized only by distortion of the features, whilst 

 those from deep-seated causes involve, in addition, a certain 

 difficulty of deglutition (deviation of the uvula, etc.) as well 

 as of hearing. 



Auditory JVerve (portio mollis of the 7th pair). This 

 is the special nerve of the organ of hearing. Its irritation can 

 only occasion sensation of sounds; its section is followed by 

 complete deafness. Its partial section in experiments on ani- 

 mals cause movements of rotation (Flourens) that have been 

 explained as caused by a vertigo of the senses (Gratiolet, 

 Vulpian). 



