550 THE NERVOUS SYSTEM. 



rence, in which blows or other injuries implicating the 

 frontal nerve as it passes over the brow, are followed by 

 total blindness in the corresponding eye. The blindness 

 appears to be the consequence of defective nutrition of the 

 retina ; for although, in some cases, it has ensued imme- 

 diately, as if from concussion of the retina, yet in some 

 it has come on gradually like slowly progressive amau- 

 rosis, and in some with inflammatory disorganisation, 

 followed by atrophy of the whole eye.* 



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 mas- 

 tication already enumerated (p. 544) ; 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 tensor 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 before 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 communica- 

 tions which, in all parts of its course, it forms with sensi- 



* Such a case is recorded by Suabilie iiithe Nederlandsch Lancet, 

 August, 1846. 



