744 THE NERVOUS SYSTEM. 



where they supply the Orbicularis palpebrarum muscle, joining with filaments from 

 the lachrymal nerve ; others supply the lower eyelid, joining with filaments of the 

 malar branch (subcutaneus malce] of the superior maxillary nerve. 



The infra-orbital, of larger size than the rest, pass horizontally forward to be 

 distributed between the lower margin of the orbit and the mouth. The superficial 

 branches run beneath the skin and above the superficial muscles of the face, which 

 they supply : some branches are distributed to the Pyramidalis nasi, joining at the 

 inner angle of the orbit with the infratrochlear and nasal branches of the 

 ophthalmic. The deep branches pass beneath the Zygomatici and the Levator labii 

 superioris, supplying them and the Levator anguli oris, and form a plexus (infra- 

 orbital) by joining with the infra-orbital branch of the superior maxillary nerve 

 and the buccal branches of the cervico-facial. This branch also supplies the 

 Levator labii superioris alseque nasi and the small muscles of the nose. 



The Cervico-facial division of the facial nerve passes obliquely downward and 

 forward through the parotid gland, crossing the external carotid artery. In this 

 situation it is joined by branches from the great auricular nerve. Opposite the 

 angle of the lower jaw it divides into branches which are distributed on the lower 

 half of the face and upper part of the neck. These may be divided into three sets 

 buccal, supramaxillary, and inframaxillary. 



The buccal branches cross the Masseter muscle. They supply the Buccinator 

 and Orbicularis oris, and join with the infra-orbital branches of the temporo-facial 

 division of the nerve, and with filaments of the buccal branch of the inferior 

 maxillary nerve. 



The supramaxillary or mandibular branches pass forward beneath the Platysma 

 and Depressor anguli oris, supplying the muscles of the lower lip and chin, and 

 communicating with the mental branch of the inferior dental nerve. 



The inframaxillary or cervical branches run forward beneath the Platysma, 

 and form a series of arches across the side of the neck over the suprahyoid 

 region. One of these branches descends vertically to join with the superficial 

 cervical nerve from the cervical plexus ; others supply the Platysma. 



Surgical Anatomy. The facial nerve is more frequently paralyzed than any of the othei- 

 of the cranial nerves. The paralysis may depend either upon (1) central causes i. e. blood-clots 

 or intracranial tumors pressing on the nerve before its entrance into the internal auditory meatus. 

 It is also one of the nerves involved in " bulbar paralysis." Or (2) it may be paralyzed in its 

 passage through the petrous bone by damage due to middle-ear disease or by fractures of the 

 base. Or (3) it maybe affected at or after its exit from the stylo-mastoid foramen. This is 

 commonly known as " Bell's paralysis." It may be due to exposure to cold or to injury of the 

 nerve, either from accidental wounds of the face or during some surgical operation, as removal 

 of parotid tumors, opening of abscesses, or operations on the lower jaw. 



When the cause is central, the sixth nerve is usually paralyzed as well, and there is also 

 hemiplegia on the opposite side. In these cases the electrical reactions are the same as in 

 health ; whereas, when the paralysis is in the course of the nerve, the reaction is usually lost. 

 When the nerve is paralyzed in the petrous bone, in addition to the paralysis of the muscles of 

 expression, there is loss of taste in the anterior part of the tongue, and the patient is unable to 

 recognize the difference between bitters and sweets, acids and salines, from involvement of the 

 chorda tympani. The mouth is dry, because the salivary glands are not secreting ; and the 

 sense of hearing is affected from paralysis of the Stapedius. When the cause of the paralysis 

 is from fracture of the base of the skull, the auditory nerve and the petrosal nerves, which are 

 connected with the intumescentia ganglioformis, are also involved. When the injury to the 

 nerve is after its exit from the stylo-mastoid foramen, all the muscles of expression, except 

 the Levator palpebrae, together with the posterior belly of the Digastric and Stylo-hyoid, are 

 paralyzed. There is smoothness of the forehead, and the patient is unable to frown ; the eye- 

 lids cannot be closed, and the lower lid droops, so that the punctum is no longer in contact with 

 the globe, and the tears run down the cheek ; there is smoothness of the cheek and loss of the 

 naso-labial furrow ; the nostril cannot be dilated ; the mouth is drawn to the sound side, and 

 there is inability to whistle ; food collects between the cheek and gum from paralysis of the 

 Buccinator. 



The facial nerve is at fault in cases of so-called "histrionic spasm," which consjsts in an 

 almost constant and uncontrollable twitching of the muscles of the face. This twitching is 

 sometimes so severe as to cause great discomfort and annoyance to the patient and to interfere 

 with sleep, and for its relief the facial nerve has been stretched. The operation is performed 

 by making an incision behind the ear from the root of the mastoid process to the angle of the 

 .jaw. The parotid is turned forward, and the dissection carried along the anterior border of the 



