THE FACIAL. 643 



time of expiration, on the other hand, it is forced outward by the exit 

 of the air. The natural movements of the nostril in respiration, are 

 therefore reversed by paralysis of the facial nerve. In the normal con- 

 dition they exhibit an active expansion in inspiration, and a partial 

 collapse in expiration. After section of the nerve the nostril collapses 

 in inspiration, and partially opens in expiration ; moving passively 

 inward and outward, like an inert valve, with the changing direction of 

 the current of the air. 



Effect on the Lips. In the lower animals generally, but especially 

 in the herbivora, the movements of the lips are mainly serviceable in 

 the prehension of the food ; and if these movements be paralyzed on 

 the two sides at once, by section of both the facial nerves, the conse- 

 quent incapacity to introduce food into the mouth may be sufficiently 

 serious to cause death by inanition. In the carnivora the motions of 

 retraction and elevation of the lips, by which the canine teeth are un- 

 covered, have also a marked effect on the expression of the face. In 

 most of these animals, after division of the facial nerve, the change in 

 the appearance of the corresponding side, even in the quiescent condi- 

 tion, is distinctly perceptible. The lips are flaccid and motionless, and 

 the corner of the mouth hangs down and cannot be completely closed, 

 owing to the paralysis of the orbicularis oris muscle. 



Effect on the Ears. In most of the quadrupeds the action of the 

 external ears is much more important than in man, owing to their 

 superior mobility and the greater development of the corresponding 

 muscles. In all, the varying position of these organs is of great influ- 

 ence in modifying the expression ; and their rapid and extensive move- 

 ments are also serviceable as an essential aid to the sense of hearing. 

 When the facial nerve has been divided, the ear on the corresponding 

 side becomes flaccid and motionless ; and in species where the organ is 

 long and narrow, as in the hare and rabbit, it can no longer be main- 

 tained in the erect position. 



All the superficial muscles accordingly of the head and face, which 

 are supplied by filaments from this nerve, are paralyzed by its section ; 

 while the sensibility of the skin, in the corresponding parts, is pre- 

 served entire. 



Facial Paralysis in Man. Facial paralj'sis, from disease involving 

 the nerve itself, its sources of origin in the brain, or the walls of its bony 

 canal in the cranium, is not an uncommon affection in the human sub- 

 ject. It is usually confined to one side, being limited by the median 

 line, and produces accordingly a marked difference in the appearance 

 of the two sides of the face. In particular cases, where the cause of 

 the difficulty is located in the branches of the nerve, certain portions 

 of the muscular apparatus may be affected to the exclusion of others ; 

 and the muscles about the lips may be paralyzed without any percepti- 

 ble loss of motion in the parts above. Or the affection may be fully 

 developed in one region of the face, and only partial in the remainder. 

 But when the disease is seated upon the trunk of the nerve within the 



