198 POULTRY DISEASES 



PARALYSIS OF THE AUDITORY NERVE OF THE FOWL 



Anatomy of the Parts 



It may be well first to give the origin and distribution of 

 the auditory nerve before taking up the disease of the same. 



In the fowl the facial (seventh pair of cranial nerves) and 

 the auditory or eighth pair, are so intimately associated, it 

 appears well to give the origin and distribution of ]:»oth at 

 the same time. 



The facial nerve originates, with the auditory, from the 

 cerebellum. It divides into three parts, the first probably 

 from the complex ganglion with the posterior roots of the 

 auditory. This root belongs to the somatic sensory group of 

 nerves. From this same group originates the auditory which 

 spreads out into the cochlea and takes the impression of sound. 

 This nerve is short and thick, and at the point where it loses 

 its medullary covering on entering the cochlea there is de- 

 veloped a ganglion. This ganglion is similar to the spinal 

 ganglion. 



The second part originates ])y one root which is located 

 medially and ventrally from the deeper ganglion cells. Some 

 of the fibers from this root constitute the vestibular branches 

 and accompany the auditory and supply the anterior part of 

 the ear labyrinth and semicircular canals. The larger part of 

 the fibers of this trunk make up the intermediate part of the 

 facial. The geniculate ganglion is formed at their fusion. 

 The sympathetic sphenopalatine nerve emerges from this gan- 

 glion, coming out of the aqueduct of Fallopius. 



The third part is called the portia dura and is the main 

 facialis. It is located opposite the auditorius intermedins, 

 its roots may be traced to the complex ganglion, from which 

 they take a ventral direction. 



Paralysis of the Cochlear Nerve 



The paralysis of the cochlear nerve, the true organ of iiear- 

 ing, may be a congenital defect and has been observed in am- 

 biotic animals. It is due to a defective condition of the spinal 

 ganglion with resulting degeneration of the organs of Corti. 

 Paralysis of the nerve may also be caused ])y inflammatory 

 changes in the internal ear or intracranial disease in the 

 neighborhood of the medulla oblongata. It has been observed 

 as a symptom in coccidiosis and also in fowl plague. 



Paralysis of the Vestibular Nerve 



This condition is frequently observed in l)irds. It is often 

 caused })y inflammation of the middle or internal ear. It has 

 been o])served in fowl pest. It is also ])i'onght a])Out in 



