68 The Cranial Nerves 



out of the flaccid corner of the mouth and he cannot arrange his lips 

 for whistling (an excellent test) ; trying if he can spit is also a useful 

 though less delicate test. Articulation is impaired, and the flabby 

 cheek is puffed out with every deep expiration. Because the bucci- 

 nator cannot contract, food lodges in the cheek, from which the patient 

 has to clear it by his finger. He has no power to draw down that 

 corner of the mouth by the action of the depressor anguli oris and 

 platysma. Loud noises become distressing because of paralysis of 

 the muscles of the middle ear. 



The soft palate and uvula are dragged from the affected side when 

 the nerve is damaged before it gives off the petrosal branches ; and, 

 the chorda tympani also being functionless, the tip of the tongue, as 

 already noted (p. 66), is drawn to the paralysed side, though not to 

 such an extent as may appear at first sight, the defect being exag- 

 gerated by the mouth being already drawn from the affected side. 

 The exact amount of the deflection of the tip of the tongue to- 

 wards the paralysed side is to be estimated by looking at the line 

 between the central incisors. The effect of the paralysis upon the 

 chorda tympani is often to pervert the taste. When the lesion is 

 below the coming off of the great petrosal the muscles of the soft palate 

 and uvula are not affected. 



Partial facial paralysis is generally due to slight haemorrhage at the 

 origin of the nerve, and when associated with rigid arteries, hypertro- 

 phied left ventricle, and retinal degeneration, is sure evidence of a 

 coming haemorrhagic storm. 



Facial paralysis is not always due to lesion at the root or of the 

 trunk of the nerve ; it may be the result of exposure near an open 

 window in a railway journey, or to a cold wind. 



Stretching. The facial, being a motor nerve, cannot be concerned 

 in facial neuralgia, but there are certain and obscure cases of facial 

 spasm in which it may be expedient to give the main trunk a specu- 

 lative jerk or two. In one such I saw my colleague Mr. Pye, operate 

 by a two-inch incision along the front of the mastoid process and the 

 topmost part of the sterno-mastoid, dividing skin, superficial fascia, 

 platysma, and deep fascia, layer by layer. Then the sterno-mastoid 

 was relaxed and drawn outwards, and, the parotid being drawn upwards, 

 the posterior belly of the digastric came into view ; along its anterior 

 border, and hurrying to the parotid gland, was the nerve, which was 

 then picked up and stretched by an aneurysm needle. 



No. 8 is the auditory nerve ; it arises in the floor of the fourth 

 ventricle, and, emerging by the groove between the olive and restiform, 

 passes down the internal auditory meatus beneath the facial. At the 

 bottom of the meatus it breaks up into branches which are spread out 

 in the cochlea, vestibule, and semi-circular canals. 



No. 9, the fflosso-pharyngreal, is distributed, as its name implies, 

 to the tongue and pharynx. It is a sensory nerve, but those fibres of 



