248 ANIMAL DENTISTRY. 



of preventing the bit from lodging against the teeth, or to 

 prevent grasping the bit between them, but this operation is 

 never effectual in palliating the lugging habit. In the young 

 horse it is harmful in that the sensitive dentinal substance 

 is thus exposed to the surface. Extraction of the first in- 

 ferior molar is likewise inefifectual. 



The veterinarian's full duty ends when all sharp points 

 are removed from the molars, and when appropriate bits 

 have been recommended. 



FACIAL PARALYSIS. 



Synonyms- — Bell's paralysis. Paralysis of the lips. Par- 

 alysis of the seventh cranial nerve. 



Definition — A partial or complete unilateral motor par- 

 alysis of the muscles controlled by the seventh cranial nerve. 



Etiology — Facial paralysis is caused by injuries to the 

 mastoid region where the seventh nerve leaves the cranial 

 cavity. The contusion is sustained by hanging in the halter 

 in the recumbent position, striking the head to the floor 

 during surgical restraint or in the struggles of painful dis- 

 eases, or from blows. 



Symptoms — The upper lip is drawn to the opposite side, 

 the corner of the lower lip is dropped so as to show its 

 mucous membrane, the nostril draws inward during inspira- 

 tion and in the severe case food will accumulate in the cheek 

 from paralysis of the buccinator. When the paralysis is par- 

 tial these symptoms are less pronounced. Bilateral facial 

 paralysis occurs occasionally when both sides of the head 

 are contused simultaneously from the above causes. In such 

 cases the symptoms presented are total inability to move 

 either lip, difficulty to retain food between the teeth and 

 audible inspirations from vapidity of the nostrils. 



Differential Diagnosis — Facial paralysis of this variety is 

 recognized from that of central origin by the sensibility of 



