THE CRANIAL NERVES. 263 



The fifth nerve is very commonly the seat of neuralgia, which 

 may affect one or all of its branches. This is called "iic 

 douloureux" or tri-facial neuralgia. The attacks come in 

 spasms, and besides the excruciating pain, there is often twitch- 

 ing of the muscles or flushing of the skin of the face. Pressure 

 at the points where the branches of the nerve come out of the 

 skull, as at the supra or infra-orbital notches, is usually espe- 

 cially painful in tic. An unhealthy condition of the teeth is 

 often responsible for the symptoms, but if dental treatment 

 and general medical care do not remove the neuralgia, it is 

 usually advisable to cut out a portion of the nerve or even to 

 remove the entire Gasserian ganglion. 



Sometimes the fifth nerve becomes paralyzed, causing anes- 

 thesia involving the area of its distribution. Tingling, numb- 

 ness or neuralgic pains often precede the anesthesia. Since the 

 conjunctiva loses its sensitiveness, particles of dust, etc., are not 

 removed from the eye by the tears so that they set up inflam- 

 mation, which may develop and cause ulceration of the cornea. 

 For the same reason, or perhaps because the nerve independently 

 controls the nutrition of tissues, the gums and cheeks may be- 

 come ulcerated and the teeth loosened. Partial loss of taste and 

 inability to smell pungent vapors, which act on sensory nerves, 

 are also common symptoms. 



THE SEVENTH^ NERVE. The seventhnerve is purely motor in 

 function. /^Tlthe facial muscles, except those TJOiMittflUid In" 

 mastication, the platysma of the neck, the posterior belly of the 

 digastric and one of the muscles of the middle ear (the sta- 

 pedius) are supplied by it. On account of its tortuous course 

 the seventh nerve is peculiarly liable to inflammation and com- 

 pression. Thus tumors or inflammation located at the base of 

 the brain may involve that portion running between the upper 

 end of the medulla oblongata and the internal auditory meatus, 

 where the nerve enters the aqueduct of Fallopius. In this 

 region it is likely to become involved when there is disease of 

 the internal ear or mastoid sinus (mastoiditis). After its exit 

 from the skull (by the stylomastoid foramen) its close association 

 with the parotid gland renders it liable to be involved in eel- 



