FACIAL, OR NERVE OF EXPRESSION 507 



As already stated, the fibres of origin of the facial have been traced 

 to the floor of the fourth ventricle, where a few decussate but most of 

 them are lost. The question now is, whether or not the fibres pass up 

 through the pons and decussate above, as the pathological facts just 

 noted would seem to indicate. Anatomical researches on this point 

 are not satisfactory; and the existence of such a decussation has not 

 been clearly demonstrated. The pathological observations neverthe- 

 less remain ; and however indefinite anatomical researches may have 

 been, there can be no doubt that lesions in one lateral half of the pons 

 affect the facial on the same side, while lesions above the pons have a 

 crossed action. The most that can be said on this point is that it is a 

 reasonable inference from pathological facts that the nerves decussate 

 anterior to the pons. 



The main root of the facial, the auditory nerve and the intermediary 

 nerve of Wrisberg pass together into the internal auditory meatus. At 

 the bottom of the meatus, the facial and the nerve of Wrisberg enter the 

 aquseductus Fallopii, following its course through the petrous portion of 

 the temporal bone. In the aqueduct the nerve of Wrisberg presents a 

 little ganglioform enlargement (geniculate ganglion) of a reddish color, 

 which has been shown to contain nerve-cells. The main root and the 

 intermediary nerve then unite and form the common trunk of the facial, 

 which emerges from the cranial cavity by the stylo-mastoid foramen. 

 It is thought by some anatomists that the intermediary nerve of Wrisberg 

 arises from the glosso-pharyngeal, which communicates with the facial 

 in the tympanum. A branch has been described going from the glosso- 

 pharyngeal to the geniculate ganglion. It has been seen that the 

 fibres of origin of this nerve come from the nucleus of the glosso- 

 pharyngeal. 



In the aquaeductus Fallopii the facial gives off the following 

 branches : 



1. The large petrosal branch is given off at the ganglioform enlarge- 

 ment and goes to Meckel's ganglion. 



2. The small petrosal branch is given off at the ganglioform en- 

 largement or a very short distance beyond it and passes to the otic 

 ganglion. 



3. A small branch, the tympanic, is distributed to the stapedius 

 muscle. 



4. The chorda tympani passes through the cavity of the tympanum 

 and joins the lingual branch of the inferior maxillary division of the fifth 

 as it passes between the two pterygoid muscles, with which nerve it be- 

 comes closely united. 



5. Opposite the point of origin of the chorda tympani, a communi- 



