THE FACIAL NERVE. 433 



corresponding eye. The blindness appears to be the conse- 

 quence of defective nutrition of the retina ; for although, in 

 some cases, it has ensued immediately, as if from concussion 

 of the retina, yet in some it has come on gradually like slowly 

 progressive amaurosis, and in some with inflammatory disor- 

 ganization, followed by atrophy of the whole eye. 1 



Physiology of the Facial Nerve. 



The facial, or portio dura of the seventh pair of nerves, is 

 the motor nerve of all the muscles of the face, including the 

 platysma, but not including any of the muscles of mastication 

 already enumerated (p. 428); it supplies, also, the parotid 

 gland, and through the connection of its trunk with the 

 Vidian nerve, by the petrosal nerves, some of the muscles of 

 the soft palate, most probably the levator palati and azygos 

 uvulae ; by its tympanic branches it supplies the stapedius 

 and laxator tympani, and, through the otic ganglion, the ten- 

 sor tympani ; through the chorda tympani it sends branches to 

 the submaxillary gland and to the lingualis and some other 

 muscular fibres of the tongue ; and by branches given off be- 

 fore it comes upon the face, it supplies the muscles of the 

 external ear, the posterior part of the digastricus, and the 

 stylo-hyoideus. 



To the greater number of the muscles to which it is dis- 

 tributed it is the sole motor nerve. No pain is produced by 

 irritating it near its origin (Valentin), and the indications of 

 pain which are elicited when any of its branches are irritated 

 may be explained by the abundant communications which, in 

 all parts of its course, it forms with sensitive nerves, whose 

 filaments being mingled with its own are the true source of the 

 pain. 



Besides its motor influence, the facial is also, by means of 

 the fibres which are supplied to the submaxillary and parotid 

 glands, a so-called secretory nerve (p. 377). For through the 

 last-named branches impressions may be conveyed which excite 

 increased secretion of saliva. For example, if, in a dog, the 

 submaxillary gland be exposed, and the chorda tympani be 

 divided, it will be seen that on stimulating the distal end of 

 the nerve by a weak electric current, the gland becomes ex- 

 ceedingly vascular, and saliva is secreted in largely increased 

 amount. Under ordinary circumstances of increased secretion 

 of saliva by the submaxillary gland, as from the presence of 



1 Such H case is recorded by Snabilie in the Nederlandsch Lancet, 

 August, 1846. 



