GOP) HANDBOOK OF PHYSIOLOGY. 



this direction, the action of the dilators and compressors of the nos- 

 trils should be perfect. 



Lastly, the sense of taste is impaired, or may be wholly lost in paral- 

 ysis of the facial nerve, provided the source of the paralysis be in some 

 part of the nerve between its origin and the giving off of the chorda tym- 

 pani. This result, which has been observed in many instances of disease 

 of the facial nerve in man, appears explicable on the supposition that the 

 chorda tympani is the nerve of taste to the anterior two-thirds of the 

 tongue, its fibres being distributed with the so-called gustatory or lingual 

 branch of the fifth. Some look upon the chorda as partly or entirely 

 made up of fibres from the fifth nerve, and not strictly speaking as a 

 branch of the facial; others consider that it receives its taste fibres from 

 communications with the glosso-pharyngeal. 



Together with these effects of paralysis of the facial nerve, the mus- 

 cles of the face being all powerless, the countenance acquires on the 

 paralyzed side a characteristic, vacant look, from the absence of all ex- 

 pression: the angle of the mouth is lower, and the paralyzed half of the 

 mouth looks longer than that on the other side; the eye has an unmean- 

 ing stare. All these peculiarities increase, the longer the paralysis 

 lasts; and their appearance is exaggerated when at any time the muscles 

 of the opposite side of the face are made active in any expression, or in 

 any of their ordinary functions. In an attempt to blow or whistle, one 

 side of the mouth and cheeks acts properly, but the other side is mo- 

 tionless, or flaps loosely at the impulse of the expired air; so in trying 

 to suck, one side only of the mouth acts; in feeding, the lips and cheeks 

 are powerless, and on account of paralysis of the buccinator muscle food 

 lodges between the cheek and gums. 



The VHIth Nerve (Auditory). 



Origin. The Vlllth nerve arises from two nuclei, median and lat- 

 eral, in the floor of the fourth ventricle, in the anterior part of the 

 bulb in front and to the side of the twelfth nerve ; it extends from the 

 middle line to the outside margin of the ventricle. There is also an 

 accessory nucleus situated on the ventral surface of the restiform body. 

 The nerve leaves the surface of the brain from the ventral surface of the 

 fore-part of the restiform body at the hind margin of the pons in two 

 roots. One winds round the restiform body dorsal to it and the other 

 passes median to it. The former is called the dorsal root. The latter 

 is called the ventral root. Most of the fibres of the dorsal root (cochlear) 

 end in cells of the accessory nucleus, but fibres emerging from this nu- 

 cleus pass inward to the bulb, superficially, forming the striae acusticce 

 in the floor of the fourth ventricle and end in the median nucleus. Most 



