458 THE CRANIAL NERVES. 



orbicularis, it is always partially open. The movements of the 

 aares are also suspended on the side of the injury, and if the angle 

 of the mouth be examined on that side, it will be found to hang 

 down lower than on the opposite side, and to be constantly partly 

 open, owing to the paralysis of the orbicularis oris and the eleva- 

 tors of the angle of the mouth. 



These are the only inconveniences which follow the division of 

 the facial nerve in the cat, but in some other of the lower animals, 

 where various muscular organs in this region are particularly de- 

 veloped, the consequences are more troublesome. Thus, in the rabbit, 

 the ear, upon the affected side, falls down, and cannot be raised or 

 pointed in different directions ; and as the movements of the ear 

 are important in these animals, as aids to the hearing, the per- 

 fection of this sense must be considerably impaired by paralysis of 

 the facial nerve. In the horse, it has been noticed by Bernard, 1 

 that division of the facial on both sides is fatal by suffocation. For 

 this animal breathes exclusively through the nostrils, which open 

 widely at the time of inspiration, to allow the admission of air. If 

 these movements be suspended, by paralysis of the facial nerve, the 

 nostrils immediately collapse, and the animal dies by suffocation. 



In the human subject, the facial nerve is occasionally paralyzed 

 upon one side, sometimes from sympathetic irritation, sometimes 

 from organic disease in the petrous portion of the temporal bone, 

 or within the cranial cavity near the origin of the nerve. In either 

 case, an extremely well-marked affection is the result, known as 

 "facial paralysis." This condition is chiefly characterized by an 

 entire absence of expression on the affected side of the face. The 

 lower eyelid sinks downward, from paralysis of the orbicularis 

 muscle, and cannot be closed. 



The corner of the mouth also falls downward, and the whole 

 lower part of the face is drawn over to the opposite side, by the 

 force of the antagonistic muscles. The lips are unable to retain 

 the fluids of the mouth ; and the saliva dribbles away from between 

 them, giving to the face a remarkably vacant and helpless appear- 

 ance. 



The principal inconvenience, however, suffered by the human 

 subject in facial paralysis, depends upon the want of action of the 

 muscles about the lips and cheek. In drinking, the fluids escape 



1 Lemons sur la Physiologie et la Pathologie du Systetne Nerveux, Paris, 1858, 

 vol. ii. p. 38. 



