722 Paralysis of the Facial Xerves. 



paralysis in these eases is probably an injury due to the animal 

 lying down for a long time or rolling, and especially in unsuit- 

 able stables. Other causes are: inflammation of the middle 

 ear, caries of the petrous temporal bone, neoplasms in the base 

 of the brain, inflammation or contusion of the pons or anterior 

 portion of the medulla, thrombosis of the inferior cerebellar 

 artery (Vosshage), etc. 



In cattle paralysis of the facial nerves sometimes results 

 from inflammation of the middle ear (Leblanc), epidermal col- 

 lections in the passage of the ear, actinomycosis in the parotid 

 region (Fuchs), tuberculosis of the brain (Fuchs). It is only 

 exceptionally that it is caused by mechanical injury, because the 

 facial nerve is protected by the horns and it is not exposed to 

 injury for half its length. Paralysis of the facial nerve follow- 

 ing parturient paresis is obviously of traumatic origin. 



Cases resulting from chill have been recorded in the dog 

 (Trossinow observed it in a dog after being brought out of 

 cold water), neoplasms in the parotid region (Gratia, sarcoma), 

 more frequently from inflammation of the middle and internal 

 ear, caries or tuberculosis of the temporal bone (Montfallet), 

 and finally encephalitis due to distemper. 



Symptoms. In cases in which all the branches of the nerve 

 are paralyzed the following symptoms are observed. Owing to 

 paralysis of the muscles of the ear that organ occupies a hori- 

 zontal position or even hangs down on the paralyzed side. In 

 dogs with naturally hanging ears it hangs over backrwards or is 

 quite normal in position, but does not show movements corres- 

 ponding to the ear of the opposite side (fig. 103). Paralysis 

 of the orbicularis palpebrarum abolishes the power of closing 

 the eye and as a result the eye remains open but the palpebral 

 fissure appears narrower than on the opposite side, or the upper 

 lid hangs down somewhat because the corrugator supercilii 

 which assists in the elevation of the lid is also paralyzed. The 

 sudden meeting of some obstacle does not result in closure of 

 the eye, but if the cornea or conjunctiva be touched the mem- 

 brana nictitans is pushed forwards, the eyeball is turned in- 

 wards and upwards showing that the inability to close the eye 

 results from paralysis of the orbicular muscle and not of the 

 trigeminus. In spite of the absence of power to close the eye 

 there is no tendency to the development of severe inflammatory 

 conditions of the cornea owing to the movements of the eyeball 

 and of the meml)rana nictitans. There may be slight turbidity 

 and even small superficial losses of tissue in cases of complete 

 paralysis. There is often lachrymation which results in the 

 loss of hair below the inner angle of the eye if it persists for 

 long. 



In contrast to what is seen in horses and cattle, the hanging of the upper 

 lid does not appear to be constant in the dog. In a case recorded by Miiller the 

 palpebral fissure on the paralyzed side was wider than normal. As a result of ex- 

 perimental section of the auriculo-palpebral nerve in a dog Marek observed marked 



