FACIAL PAEALYSIS. 203 



nerve in such a position as to involve the trunk between the point 

 where the chorda tympani joins it and the point where the great 

 superficial petrosal nerve leaves the geniculate ganglion, since 

 the taste fibres leaving the facial nerve pass by the petrosal nerve 

 to enter the brain by way of the fifth nerve. (Fig. 18, p. 199.) 



In the adult the trunk of the facial nerve emerges from the 

 stylomastoid foramen in a protected position, but in the infant 

 the opening of the canal is practically exposed on the lateral 

 aspect of the skull and is liable to injury by the forceps during 

 delivery. The posterior auricular branch, which supplies the 

 retrahens aurem and the occipitalis muscles is given off imme- 

 diately after the exit of the nerve, so these muscles occasionally 

 escape when the nerve is injured near the mandible by wounds 

 or direct violence. The nerve trunk enters the parotid gland just 

 above the level of the tip of the lobule of the ear, hence it may 

 be involved by parotid tumours or inflammations, or by vertical 

 incisions into the gland carried above the level indicated. The 

 nerve had also been compressed by gummatous and lymphatic 

 glandular swellings in this region and injured by operations 

 undertaken for removal of the latter. The exposed position of 

 the filaments of distribution on the face is no doubt a contributing 

 factor in the production of the ordinary or so-called rheumatic 

 type of facial paralysis. It is doubtful whether the usual explana- 

 tion that the nerve is compressed in the aqueduct of Fallopius 

 on account of its own swelling is a valid explanation of the 

 production of this form of palsy. 



Although the facial nerve is usually considered and described 

 as purely motor in function certain sensory symptoms may 

 accompany facial paralysis. The defect of taste on the fore part 

 of the tongue has already been mentioned. There may also be 

 some defect of smell on the paralysed side, which may be 

 attributed to weakness of the sniffing movements of the nostril 

 on that side. Defect of hearing when present may be due to 

 inflammation of the tympanum or to simultaneous implication 

 of the facial and auditory nerves at the base of the brain. When 

 the stapedius muscle is paralysed the unbalanced action of the 



