The Nervous System. 287 



the middle ear, emerges and supplies the submaxillary gland 

 with sensory fibres derived from the fifth, and secretory and 

 vaso-dilator fibres (see p. 105) . The chorda also possesses 

 taste fibres for the margin and tip of the tongue, which it 

 reaches through the lingual ; these taste fibres are probably 

 derived from the glossopharyngeal. 



The other branches of the facial are distributed as motor 

 fibres to the muscles of the face (those of expression, not of 

 mastication), also to the muscles of the ear. 



Division of the seventh nerve leads to alterations in sight, 

 taste, hearing, smell, and facial expression. As it supplies 

 the muscle which closes the eyelids, the orbicularis palpe- 

 brarum, conjunctivitis occurs from exposure of the eyeball ; 

 hearing is affected owing to paralysis of the muscles of the 

 internal ear ; smell is impaired owing to the paralysed con- 

 dition of the nostrils ; taste is affected through paralysis of 

 the chorda. 



The expression of unilateral facial paralysis in the horse 

 is characteristic ; the upper lip drawn to one side, the 

 elongated nostril, the pendulous lower lip, escape of saliva 

 and food from the mouth, the vacant look and the drooping 

 ear, point clearly to the extensive distribution of this nerve. 



Eighth Pair, or Portio Mollis. — Arises by two roots : one 

 the nerve for the special sense of hearing, the other dis- 

 tributed to the semicircular canals, and assists through 

 these in maintaining the equilibrium of the body (see 

 ' Cerebellum '). 



Injury to the semicircular canals produces giddiness, not 

 deafness, and certain movements (termed ' pendulum-like ') 

 of the head occur ; the direction in which these are made 

 depends on the direction in which the canals have been 

 injured. 



Ninth Pair, or Glosso-Pharyngeal, is a mixed nerve, though 

 at its origin it is described as a sensory one. It supplies 

 motor power to the muscles of the pharynx, and sensory 

 fibres to the posterior third of the tongue, soft palate, part of 

 pharynx, and anterior surface of the epiglottis. It is also a 

 special nerve of taste, supplying the posterior third of the 



